Field help (PFIDEFVAL) 

The default value is in folder currency and defined upon setup. It corresponds to the default value initialized when choosing the invoicing element in the Supplier record.
It can be modified at the level of the BP record. This last value is the one that will be used in the orders and invoices.
If an invoicing element is manually associated with a supplier invoice, the default value will come from the invoicing element converted to the invoice currency.
When an invoicing element is used at the structure code level (for the line elements), it cannot be defined at the supplier record level. The value of this element will be calculated at document level by using the charge or discount column dedicated to its loading.