No, This will make it work:
game.Players.PlayerAdded:Connect(function(Plr)
local stats = Instance.new("Folder", plr)
stats.Name = "leaderstats"
local ValueName = Instance.new("IntValue", stats) -- Will insert a intvalue into stats.
ValueName.Name = "ValueName" -- Will name the value
ValueName.Value = 0 -- How much the player starts off with.
while true do
wait(1)
ValueName.Value += 1
end)
end