for i = 0, 10 do game.StarterGui.Cloaking.Frame.CloakingTime.Size.Y = game.StarterGui.Cloaking.Frame.CloakingTime.Size.Y - (0; 18) wait(1) end
Well, I don't know how to subtract from UDim2.
Try this
game.StarterGui.Cloaking.Frame.CloakingTime.Size=UDim2.new(0,0,0,game.StarterGui.Cloaking.Frame.CloakingTime.Size.Y.Offset-i)