[Adapt]

Originally Posted by Ketho You need to wait until ADDON_LOADED until your savedvariables are available https://wow.gamepedia.com/Saving_var..._game_sessions ...

Thanks for your kind help and quick response. Does this mean that any logic in relation to interacting with that variable needed to come after that event has fired?

i.e.

local Congrats_EventFrame = CreateFrame("Frame")
local defaults = {
    TotalXP = 0
}
 
Congrats_EventFrame:RegisterEvent("ADDON_LOADED")
Congrats_EventFrame:RegisterEvent("CHAT_MSG_COMBAT_XP_GAIN")
Congrats_EventFrame:SetScript("OnEvent",
    function(self, event, ...)
        if event == "CHAT_MSG_COMBAT_XP_GAIN" then
            local arg1 = ...
            local xpgained = string.match(string.match(arg1, "%d+ experience"), "%d+")
        
            print('--xp gained--')
            print(UnitLevel("player"), xpgained, date("%d/%m/%y %H:%M:%S"))
            print('---')
 
            -- this doesn't seem to get saved or displayed?
            XPLogger.TotalXP = XPLogger.TotalXP + tonumber(xpgained)
            print('Total XP' .. XPLogger.TotalXP)
        elseif event == "ADDON_LOADED" then
            local addon = ...
            if addon == "XPlogger" then
                print('XPLogger loaded')
                XPLogger = XPLogger or defaults
                self:UnregisterEvent(event)
            end
        end
    end)