PO condition value is NOT ZERO before price is maintained during ME21N

PO condition value is NOT ZERO before price is maintained during ME21N. Normally condition price should show as zero before price per unit is maintained; and updated when quantity x price per unit exist.

This is a non material PO using AAG = K. Hence there're no PIR and contract.

Screenshot as follows :
Problem PO : screenshot 1

Normal PO : screenshot 2

Thank you.