I'm getting this error:
20:30:41.764 - Workspace.PlayerScript:18: attempt to perform arithmetic on local 'newValue' (a table value)
local DataStore = game:GetService("DataStoreService"):GetDataStore("DataStorage")
game.Players.PlayerAdded:connect(function(player)
local key = "user_" .. player.userId
DataStore:UpdateAsync(key, function(oldValue)
local newValue = oldValue or 0
newValue = newValue + 20
return newValue
end)

2 comments
are you trying to load in a players stats? or save?
I'm trying to save AND load when the player enters.