Prepayment matching with PO

Summary:

Content (please ensure you mask any confidential information):

We have a used case where the user is trying to match a prepayment with a purchase order having billing invoice match option receipt and match approval level 3 way, but system is not showing any quantity to match.

Moreover, if this is not possible, we need to know the way out how we can make sure that a standard invoice matched with a po will have only required prepayments available to apply because user is making no of prepayments which he does not wants to apply on standard invoice.(to restrict only to required prepayments available which user wants to apply not all the available prepayments)