Object Library in the P4072?

We are trying to use Basis code 8 for procurement to create the Order level functionality.  We have been able to find a lot of information out there regarding basis code 8 and one of the things that we found was that we had to populate the Object Library field in the P4072.  The question is what is this field, there is no logic behind it except to throw a blanks invalid error, meaning I can put 123 in this field and nothing happens, it allows us to save the adjustment.  We are also trying to determine where to add