You've probably noticed a column in the Real_Commitments table called Paid_Up. The table design describes it as:
"Y or N. A fully paid-up indicator, which a batch SP will periodically set to Y for all commitments that have been fully paid up. This indicator will be set to N on insert and whenever PAYMENTS records are created against that REAL_COMMITMENTS record."
When you try to do some reporting and look at what you've paid against a commitment and what's still left to pay, this column flag might not make sense.
You might have picked a commitment, calculated what you think you should have paid, and then looked at the sum of all payments made for that commitment. Even when these amounts are the same, the field "PAID UP" in the real commitments table says "N."
This is because the Y/N Paid_Up flag has never been used since it was added. It was intended for future use, but that never happened, so it's there without an active purpose at the moment.
To triangulate your investigations, you can also use the B13 reports in the Reports Repository to double-check your payments vs. planned. There's also a report called 'Unpaid Commitments' in the Payments subfolder of the Finance subfolder in the Reports Repository. This report will show all the commitments and what's left to pay on those commitments.
You might want to obtain the report SQL from the Admin Tool and tweak it to match your needs if you have that capability within your business.