Hello Ray,
I'm replying through the first few lines of your discussion. Usually this happens because of the over-riding of system calculations based on Annual estimate figure given by you. See these useful links and other to understand the behaviour of Annual Estimate figure in the Counter.(IK03).
Behavior of Performance Based Plan in SAP Plant Maintenance
Performance based Maint Plan and annual estimat... | SCN
Good luck
KJogeswaraRao