Wait() doesn't works or works but not properly in RunServices?

RS.RenderStepped:Connect(function()
	if KeyHeld == true then
		if sec < 10 then
			sec = sec + 1
			print(sec)
			wait(0.5)
		end
	else
		sec = 0
	end
end)

basiaclly I'm trying to make some kind of held down key triggers where it checks for how long it being held down in 0.5 seconds, but for some reason wait(0.5) doesn't works in here and it just adds 1 to sec immediately without waiting