Associate a supplier prepayment to a PO in %

Hello,

I created a purchase order for a total amount of 5.000 €

The supplier sends me an invoice for 30% of the total amount of the PO

I register a ‘prepayment’ type invoice and wants to associate it with the PO

I insert the PO number in the field ‘Identifying PO’ and all other information necessary

Then, I select ‘match invoice lines’ but at this point, I can only insert an amount

I’d like to know if it is possible to insert a %

Many thanks for your help

Best regards