Column Explanations for P43230 Cost Analysis?

If I enter a Supplier into the P43230 Cost Analysis, I can see a Percent Cost Variance in one specific month. However, if I view the details for that month, none of those associated records have a variance, or even a rounding issue. Where is this variance coming from?

Also, how are the Ordered Unit Cost and Received Unit costs in P43230 calculated for each month? It is not displaying a total or an average.