Advance Percentage& Recoupment Rate in Complex PO Line

Dears,

I have entered 50% advance percentage for a PO line. And when I enter 60% recoupment rate, It seems to me that there would be an overrate amount.

Ex.:

PO Line Amount = 12000 $

Advance Percentage = 50%

Recoupment Rate = 60%

so in the end, the prepayment amount would be 6000$ and the recoupment amount would be 7200$.

So, Should I enter recoupment rate that is equal to advance percentage to void differences?

And are there business situations that requires the recoupment and advance to be in different rates (which explains why it is designed this way in the application)?

Thanks