Expense Report Lines marked as DNC

We have several expense report lines that show a status of DNC.  It appears one of the lines was denied and was flagged as a duplicate line from another expense report.  However, all of the other lines with the exception of one are marked as DNC, and no reason is listed to indicate a reason.  The remaining line is shown as paid and the expense report payment was only for the amount of that line.  I'm not familiar with the DNC status and how that is assigned, as opposed to the DEN status.  Since the lines marked as DNC were