Trying to make 2 leaderstats

Something else must be editing the leaderstats since the script you made works fine for me, I also modified it a bit so its shorter. You should also be using task.wait() since wait() is going to get deprecated, more info on the announcement of the task library.

game.Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new("Folder")
	leaderstats.Name = "leaderstats"
	leaderstats.Parent = player

	local timeingame = Instance.new("IntValue")
	timeingame.Name = "Time"
	timeingame.Parent = leaderstats

	local towers = Instance.new("IntValue")
	towers.Name = "Towers Completed"
	towers.Parent = leaderstats
	
	while true do
		task.wait(1)
		timeingame.Value += 1
	end
end)

(Both your original script and my modified version work for me)
I’ll also just throw in a screenshot.
image