WowAce

So, for quite some time now I've been look for a way to add decimal commas to large numbers, huge QoL improvement for me.

With that in mind i looked online how to create a custom tag and come across this code :
http://lua-users.org/wiki/FormattingNumbers

function comma_value(n) -- credit http://richard.warburton.it
	local left,num,right = string.match(n,'^([^%d]*%d)(%d*)(.-)$')
	return left..(num:reverse():gsub('(%d%d%d)','%1,'):reverse())..right
end

Have in mind that i know almost nothing of coding, tried my best to figure it out how to add that to a new text tag, asked in some discords and a friend came up with this

function(unit)
    function comma_value(n) -- credit http://richard.warburton.it
        local left,num,right = string.match(n,'^([^%d]*%d)(%d*)(.-)$')
        return left..(num:reverse():gsub('(%d%d%d)','%1,'):reverse())..right
    end
    if( UnitIsDead(unit) ) then
        return ShadowUFLocals["Dead"]
    -- Unit is dead, and they have released
    elseif( UnitIsGhost(unit) ) then
        return ShadowUFLocals["Ghost"]
    -- Unit is no longer online
    elseif( not UnitIsConnected(unit) ) then
        return ShadowUFLocals["Offline"]
    else
        return string.format("%s/%s", comma_value(UnitHealth(unit)), comma_value(UnitHealthMax(unit))) 
    end    
end 

 Works fine till i relog, then i get this lua errors 

1x [string "return function(unit, unitOwner)..."]:13: attempt to index global 'ShadowUFLocals' (a nil value)
[string "return function(unit, unitOwner)
    function comma_value(n) -- credit http://richard.warburton.it
        local left,num,right = string.match(n,'^([^%d]*%d)(%d*)(.-)$')
        return left..(num:reverse():gsub('(%d%d%d)','%1,'):reverse())..right
    end
    if( UnitIsDead(unit) ) then
        return ShadowUFLocals["Dead"]
    -- Unit is dead, and they have released
    elseif( UnitIsGhost(unit) ) then
        return ShadowUFLocals["Ghost"]
    -- Unit is no longer online
    elseif( not UnitIsConnected(unit) ) then
        return ShadowUFLocals["Offline"]
    else
        return string.format("%s/%s", comma_value(UnitHealth(unit)), comma_value(UnitHealthMax(unit))) 
    end    
end "]:13: in function `func'
[string "@ShadowedUnitFrames\modules\tags.lua"]:232: in function `UpdateTags'
[string "@ShadowedUnitFrames\modules\layout.lua"]:444: in function `InitFontString'
[string "@ShadowedUnitFrames\modules\layout.lua"]:466: in function `SetupText'
[string "@ShadowedUnitFrames\modules\layout.lua"]:144: in function `Load'
[string "@ShadowedUnitFrames\modules\units.lua"]:303: in function `SetVisibility'
[string "@ShadowedUnitFrames\modules\units.lua"]:605: in function <ShadowedUnitFrames\modules\units.lua:435>
[string "=[C]"]: in function `SetAttribute'
[string "@ShadowedUnitFrames\modules\units.lua"]:956: in function `LoadUnit'
[string "@ShadowedUnitFrames\modules\units.lua"]:1329: in function `InitializeFrame'
[string "@ShadowedUnitFrames\ShadowedUnitFrames-v4.2.8.lua"]:263: in function `LoadUnits'
[string "@ShadowedUnitFrames\ShadowedUnitFrames-v4.2.8.lua"]:86: in function `OnInitialize'
[string "@ShadowedUnitFrames\ShadowedUnitFrames-v4.2.8.lua"]:907: in function <...aceShadowedUnitFrames\ShadowedUnitFrames.lua:905>

Locals:
unit = "target"
unitOwner = "target"
(*temporary) = nil
(*temporary) = "target"
(*temporary) = false
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = "attempt to index global 'ShadowUFLocals' (a nil value)"

3x ShadowedUnitFrames\modules\auras-Auras.lua:658: attempt to index field 'buffs' (a nil value)
[string "@ShadowedUnitFrames\modules\auras-Auras.lua"]:658: in function <ShadowedUnitFrames\modules\auras.lua:649>
[string "@ShadowedUFFacade\ShadowedUFFacade-1.5.3.lua"]:67: in function <ShadowedUFFacade\ShadowedUFFacade.lua:65>
[string "@ShadowedUF_NotMyAuras\ShadowedUF_NotMyAuras-v0.1.1.lua"]:125: in function `?'
[string "@ShadowedUnitFrames\modules\units.lua"]:36: in function `FullUpdate'
[string "@ShadowedUnitFrames\modules\units.lua"]:370: in function `CheckUnitStatus'
[string "@ShadowedUnitFrames\modules\units.lua"]:226: in function <ShadowedUnitFrames\modules\units.lua:223>
[string "=[C]"]: in function `Show'
[string "@FrameXML\SecureStateDriver.lua"]:83: in function <FrameXML\SecureStateDriver.lua:73>
[string "@FrameXML\SecureStateDriver.lua"]:137: in function <FrameXML\SecureStateDriver.lua:119>

Locals:
self = <table> {
 OnDisable = <function> defined @ShadowedUnitFrames\modules\auras.lua:17
 updateButton = <function> defined @ShadowedUnitFrames\modules\auras.lua:219
 UpdateFilter = <function> defined @ShadowedUnitFrames\modules\auras.lua:488
 scan = <function> defined @ShadowedUnitFrames\modules\auras.lua:588
 OnConfigurationLoad = <function> defined @ShadowedUF_NotMyAuras\ShadowedUF_NotMyAuras.lua:140
 OnEnable = <function> defined @ShadowedUnitFrames\modules\auras.lua:7
 OnLayoutApplied = <function> defined @ShadowedUnitFrames\modules\auras.lua:327
 moduleKey = "auras"
 moduleName = "Auras"
 Update = <function> defined @ShadowedUF_NotMyAuras\ShadowedUF_NotMyAuras.lua:119
 anchorGroupToGroup = <function> defined @ShadowedUnitFrames\modules\auras.lua:617
}
frame = SUFUnittarget {
 0 = <userdata>
 OnEnter = <function> defined @ShadowedUnitFrames\modules\units.lua:662
 UnregisterAll = <function> defined @ShadowedUnitFrames\modules\units.lua:140
 isDead = false
 auras = <table> {
 }
 registeredEvents = <table> {
 }
 UnitClassToken = <function> defined @ShadowedUnitFrames\modules\units.lua:677
 powerBar = <unnamed> {
 }
 RegisterNormalEvent = <function> defined @ShadowedUnitFrames\modules\units.lua:62
 SetVisibility = <function> defined @ShadowedUnitFrames\modules\units.lua:241
 topFrameLevel = 5
 RegisterUpdateFunc = <function> defined @ShadowedUnitFrames\modules\units.lua:113
 SetBlockColor = <function> defined @ShadowedUnitFrames\modules\units.lua:186
 unitType = "target"
 SetRangeAlpha = <function> defined @ShadowedUnitFrames\modules\units.lua:174
 visibility = <table> {
 }
 indicators = <unnamed> {
 }
 unitInitialized = true
 unitRealType = "target"
 unit = "target"
 ReregisterUnitEvents = <function> defined @ShadowedUnitFrames\modules\units.lua:41
 fontStrings = <table> {
 }
 unitGUID = "Player-3209-09025FB4"
 hasStateWatch = false
 RegisterUnitEvent = <function> defined @ShadowedUnitFrames\modules\units.lua:107
 comboPoints = <unnamed> {
 }
 altPowerBar = <unnamed> {
 }
 emptyBar = <unnamed> {
 }
 healAbsorb = <unnamed> {
 }
 unitEventOverrides = <table> {
 }
 auraIndicators = <unnamed> {
 }
 highFrame = <unnamed> {
 }
 UnregisterSingleEvent = <function> defined @ShadowedUnitFrames\modules\units.lua:90
 DisableRangeAlpha = <function> defined @ShadowedUnitFrames\modules\units.lua:166
 OnLeave = <function> defined @ShadowedUnitFrames\modules\units.lua:670
 fullUpdates = <table> {
 }
 UnregisterUpdateFunc = <function> defined @ShadowedUnitFrames\modules\units.lua:130
 isUnitVolatile = true
 BlizzRegisterUnitEvent = <function> defined =[C]:-1
 healthBar = <unnamed> {
 }
 FullUpdate = <function> defined @ShadowedUnitFrames\modules\units.lua:33
 SetBarColor = <function> defined @ShadowedUnitFrames\modules\units.lua:182
 unitOwner = "target"
}
config = <table> {
 height = 0.500000
 debuffs = <table> {
 }
 buffs = <table> {
 }
}
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = "attempt to index field 'buffs' (a nil value)"
scan = <function> defined @ShadowedUnitFrames\modules\auras.lua:588
anchorGroupToGroup = <function> defined @ShadowedUnitFrames\modules\auras.lua:617

 Can you help me figure out how to fix this? or a better way to add the decimal comma?

ShadowUFLocals is not a thing, replace it with ShadowUF.L,  eg. ShadowUF.L["Ghost"]