Understanding Customer Maintenance Demand Tab Unit Price Difference

We just implemented EDI about a month ago and seems to be working properly. I do have a question about how the Unit Price Difference works. We set up our Customers or Trading Partners to STOP the EDI process if there is a Unit Price difference and with zero tolerance. it seems to only work if the unit price is less than our selling price. It doesn’t create a Sales Order and will be Rejected by the System. However, it creates the SO if the unit price is over or more than our selling price. We need it to only create the SO if it’s exactly the same price. Does the system only stops it when it’s less? Any ideas how to stop it either way? Thank you.

Epicor 10.2