Internal Order GL Posting

Hi,

I am creating a GL account and i assigned it to my PO

When i do PO, entry passed is: Internal Order Expense A/c.... Dr

To GRIR Account.

When i ran settlement, entry passed was: Asset A/c... Dr

To Internal Order Expense A.c

I want to know where do we assign the GL account to Internal Order i.e. how internal order determines GL Accoiunt (Sender GL Account) at the time settlement