BCS Breakdown Check - how to adjust individual records?

Hi all,

I just arrived at a new client and have found several thousand inconsitent records.

Breakdown check shows us how many there are and also allows entry of a vlue for missing subassignments.

However, there is no option to adjust individual lines (not even to differentiate between totals records and journal entries), eg Item 800210 now requires breakdown by Partner Unit, however, there are 15 records with a blank value but only one line in breakdown check in which to enter a partner.

Obviously the user wants to enter different partners depending on further details (eg cons unit, amount, other breakdown values etc.),

where/how can such selections be made?