Approval Routing for Vendor Bills (2 way match)

Hi There

I have never set up 3 way match before.

The scenario I have:

Multiple vendor bills will be received for a single purchase order.

There are no physical goods or item receipts.

There is a 2% tolerance set up on the vendor record for amount.

Does 3 way match compare a single vendor bill to its corresponding purchase order when deciding whether the bill needs to be routed for approval?

Or, like in this scenario, does it look at the cumulative total of all vendor bills and compare this to the purchase order to decide whether the cumulative total of all vendor bills matches the purchase order?