Field help (PBSSTR) 

Mention in this column the account roots from which the reporting codes are assigned. If several lines in the table can correspond to the same account, it is always the lines whose root is closest to the account that is applied. For instance, with the following setup:
Root        Code if Debit      Code if Credit
7 AA AA   70 AB AB           712 AD AD
               71 AC AC   
the result is: 712300 AD AD
                   707100 AB AB
                   721000 AA AA