Why does the summary of unmatched cash book items show a negative balance, even though there are no unmatched items listed on the reconciliation?

When revisiting locked bank reconciliations, it is important to note that the summary page is taken from the point at which the bank reconciliation was submitted. At the time of submission there may have been unmatched bank items; however, they could since have been matched in a later bank rec and would therefore not appear within the unmatched tab anymore.