Net Debit Posting Fields F0902

Hello,

What are the net debit posting fields in the F0902 used for?  I've noticed that sometimes they're populated, sometimes they're not.  Sometimes all negative amounts from the Net Posting (AN01-AN14) are moved over to the Net Debit Posting fields, but sometimes all of the negative amounts stay in the Net Posting fields.

I'm noticing inconsistencies when I run the annual close (R098201), and the amounts are often equal to some of the amounts in the Net Debit Posting fields.

Is there some setting that determines if these fields are used or not?  Or do only certain processes use them?