Approve Blanket Purchase Agreements, How to assign an approval group to limit approval of BPA?

Oracle 12.2

It appears that if the "amount agreed" is left blank the ability to self approve BPA's is simply a True/False in whether they have the "Approve Blanket Purchase Agreements" added to their approval assignment. Whether it is 1 dollar or UNLIMITED doesn't matter they can self approve. The amount only seems to matter if "amount agreed" has a value entered, if left blank then as long as they have Approve Blanket Purchase Agreements they can self approve.

I tested granting unlimited and 1K approval groups, adding items and pricing, the BPA self approved. The approval limits only mattered when an "amount agreed" was entered, but this is not required. and leaving blank is like having unlimited approval authority. We had hoped the approval amount was driven off changing in item price or adding additional items to the BPA.