Tweening Timer correcly

Hello together,
I want to Tween my progress bar correctly according to the time values given, but I just cant do the math. Can anyone help?

rewMax = (seconds+(minutes*60))
rewBar:TweenSize(UDim2.new(rewBar.Size.X.Scale + 1/rewMax, 0, rewBar.Size.Y.Scale, 0), Enum.EasingDirection.Out, Enum.EasingStyle.Sine, 0.1, false)