OBYC Setting-GBB

I am stuck with the OBYC Setting.

I fail to understand which GL accounts have to be used for GBB transaction under ZOB modifier.

ZOB is used for Good Receipt without Purchase Order. So I understand that the tansactions involved are BSX & GBB, correct ?

So BSX, inventory account is used. However, which GL account (description) I should use for GBB -ZOB setting ? If anybody can guide me with the accounting entries for this movement type 501 (GR without PO), It would be an excellent help for me.