Cleaning up very old Purchase Orders and Requisitions before the upgrade

I'm new to this organization.  They use budget (encumbrance) accounting.  It seems in the past that they have a fairly large number of open encumbrances.  Sitting next to these encumbrances in the table are manual encumbrances that appear to be someone's attempt to clean off the old encumbrances.  Has anyone seen this?  I would like to be able to naturally close/finish the old POs while reversing those manual encumbrances.  Then our encumbrance reports would be correct and clean.

Thank you,

John