Dynamics GP - negative CR amounts in PR distribution

I was trying to balance a custom payroll report I created to the GL and was narrowing the differences when I suddenly realized what I was looking at: In reviewing the UPR30401 table (Payroll Distribution Detail) I saw negative credit amounts.

I had to rub my eyes as I could not believe what I was seeing.  This is Dynamics GP 2010 and the client runs weekly payrolls and has been for years.

I was pulling numbers from UPR30401 and was trying to balance to the GL but could not resolve the difference.  When I drilled down on an account for a specific period I noticed the negative credit amounts in the table.  In order to get the difference resolved I had to use the absolute value of the credit column in that table.  The related GL entry shows a positive credit amount (or has the positive credit subtracted from the debits for summary postings.)

This is completely unexpected behavior of GP and something I will have to watch if I use that table again.  I've never seen negative credits anywhere else in GP, in fact GP avoids negatives in most situations completely.

Again BEWARE if you are using the UPR30401 take the absolute value of the credit column (CRDTAMNT.)