PO and mfg variance calculations (PPV)

SOLVED

I'm trying to understand exactly what is in the  the PPV amounts (and how calculated) on our Sage income statement so we understand the information reported, if the manual JE's are correct,a and if we need to change our processes. 

We have two GL accounts, one  for PO Variance and the other is mfg Variance in sage 100.  How are these balances calculated in Sage?  For a given item on a Sales Order and invoice posted in a given time period (ie month),  is it the Standard Cost minus the PO amount for that specific item?  Does it exclude items on vendor  PO's received (and/or invoiced) during that time period? does it include the difference between the actual vendor invoice amount paid and the vendor PO amount for an item?  

Any help is appreciated!  Thanks!