AR refunds attributes screen

this question is about the AR refund attributes pop up screen.

If the user does not populate the payment terms, payment method, priority where does the attribute form pick them up from.
How to set up default , payment terms ., priority and payment method for a refund attribute form?

My problem is that I have a customer with payment terms as immediate on his profile as well as on the transaction.
If I don't populate the payment terms on the refund attribute form the refund makes it 30 days net.

Why 30 days and where do these default come from?
 

Problem Description: AR refund attribute form fields s paick up many attributes from Customer set ups .