Marginal Accessorial Cost not calculating as expected

I am trying to set up a marginal accessorial cost for packages over 3 in a shipment.  I was fairly certain I had used this before successfully, but my current accessorial is calculating the cost against all packages in the shipment instead of just the packages over 3.  So, for example, in a shipment with 15 packages, I would expect a calculation of $1.25 * 12 packages, but instead OTM is calculating $1.25 * 15.  Does anyone have an idea what I might be doing wrong?  My accessorial setup is in the attached pic.