Return to vendor via delivery customer master

Hi Gurus,

I am doing the return delivery to vendor(122) via delivery.

Now when I am creating the vendor and selceting Returns vendor and shipping

condition sytem (and account group for customer) is creating a customer master in

the background.

Now when I am seeing the customer master XD03 it is created with general data and

Sales Org data.no comapany code data is created.

And I can find that this customer is created for

Sales Org 1000

Dist. Chn 10/12/00

Now my question is why only this 3 combination is created and how it is determined

or where we maintain this in customization.

Thanking you