Tax Rate Variance (Payables invoice)

Summary:

Trying to understand where the amount comes from on accounting entries on AP invoice

Content (required):

I have a retainage release AP invoice (1,603.73$) matched to a PO (439,676.70$) and a Tax Rate Variance line in accounting (4.99$). I am tring to understand where this 4.99 is coming from - I read the following on Oracle support: "When invoice has tax and PO does not have Tax, Tax Rate Variance will be generated in place of 'Non rec Tax distribution'. "

In my example, PO does have taxes.

I appreciate any input in clarifying this

Version (include the version you are using, if applicable):