Co-product defaulted as item in component list of order

Hi Mates,

I am creating a process order for a co-product A which has 1 co-product as its BOM component B .  But when i create a process order I find both A and B in material list of process order. How A is coming in material list when it is not part of BOM component or recipe material list. Is there any configuration ? I don't want A to appear in material list.

Also when i want to do GR for item B using a BAPI BAPI_GOODSMVT_CREATE it ends up with error.

Thanks in Advance