Field POSAR in VBAP is showing as Blank and VBRP is showing as A, Please explain the reason?

Dear All

In billing documents, value of field POSAR-VBRP is showing as 'A' ( value item ) even though the field value of VBAP-POSAR as blank ( standard item) in the corresponding sales document ( contract document). Please explain the reason and possible customizing and enhancement objects to control the above setting. What would be the reason?

Note: 1. item category customization configured as standard items (blank). And there is no change in the item category settings.

1. 2. Due to the above issue, the sales quantity field is not updating in CO-PA document at value fields level.

Please explain the reason.

Thank you for your valuable contribution and time on this error.

Regards Gopalreddy