I had a problem when I made one payment from my bank account against two invoices - one invoice was already partially paid.
Whe match routine ONLY shows the total amount of each invoice you can assign the payments to - so you need to know how much the unpaid balance is, which can be difficult if a supplier has several outstanding and partially paid invoices.
It was not even clear that I could amend the amount to match the payment against each invoice!
Surely the matching screen should show the unpaid balance on each invoice, rather than the total value of the invoice whether it is partially paid or not!