AN8 Address Number on OK orders

We are setting up intercompany orders.

After entering the SI order and ship confirming it, the R4210IC is run creating the SK and OK orders.

I am puzzled where the AN8 on the OK order comes from.  R4210IC --> asks for a version of the P4210 which in turn looks to a version of the P4310.

Allthough in this version is stated that the address should come frome the Business Unit Table the adress of the Branch/Plant is taken which causes the invoice to be generated under the number of the Branch/Plant the goods are send from instead of putting it all under one company number.