DBM Vehicle Order Accounting Document issue

Hi Experts,

I have assigned one Balance Sheet Account for one of the line item in DBM Vehicle order, while creating billing document the Balance sheet GL account is showing the Internal Order number in order field. Could you please provide some inputs on what basis this Order is getting populated in Accounting document screen. Highlighted(yellow color) order number should not updated here. Please find below screen shot.

Thanks & Regards

vijay