Need a Prepayment and standard Invoice amount difference clarity

HI.

I have a scenario regarding prepayment and standard invoices. For example. I created a prepayment invoice in the amount of 10,000 to the supplier and payment was also done. After that, the supplier gave me an invoice in the amount of 8,000. and he insists on being fixed on 8000. but I have paid a prepayment in the amount of 10,000. The thing is the difference of 2000 is available in the system and how i will record that 2000 amount in Oracle Fusion?