We took the time this month to zero in on why we have to make adjustments to Received Not Invoice account.  Here is what we found:
Sometimes we would get different amounts when running the report.  What is happening is that if an invoice is processed in the next month for an RNI item in the previous month and the AMOUNT IS CHANGED, the changed amount hits the report, but doesn't hit GL until the following month. It is more a timing issue than anything.
 
Example:   Vendor XYZ   RNI:  $300 in Nov.
                 Process the actual invoice on Dec. 3 for $250
                 RNI report run for Nov. (but run after Dec.3)
                   shows $250 not $300.
                 However, GL transaction for Nov. have
                   the $300

Not seeing a list of price changes at the end of my report.  Is there a setting I need to change so they show up?