How is "Price" invoice hold based/computed if we set a Price Percentage Invoice tolerance as "Zero"?

Summary:

We would like to know how "Price" invoice hold is based/computed if we set a Price Percentage Invoice tolerance as "Zero".

Content (required):

Hi, we encountered an issue wherein the PO line was received with a different UOM code. Thus, it resulted to a Price invoice hold when matched to an Invoice. This scenario was fully invoiced PO, and we have a Zero invoice tolerance setup for Price Percentage.

However, when we tried doing a partially received and invoiced PO, the invoice Hold is not occurring for this Invoice.

We would like to know how the Price tolerance is to be computed under this scenarios.