Formatting a time difference to work in a pivot table

OK.... I'm calculating the delay in a patient receiving a certain procedure at my facility. From my spreadsheet I have arrival time, and procedure time, and I've formatted my "delay" box as =(d2-c2)

Easy

Now I need a Pivot table to highlight this data per pt visit by month, so I create a pivot table, but when I try to place my "delay" into the pivot table it inserts a time (12:01:00 AM) instead of a count of minutes ( 0:01). My delay colum is formatted as custom (hh:mm).

Is there a way within the pivot table to change the number formatting, or have I missed something else?

Sorry I can't share my spreadsheet. HIPPA