in business rule , it cannot valuate the value in iteration?

We have a customized doctype with iterated PIDgrp, so I have a rule that needs to evaluate the pv1:3.1 value to decide which operation the HL& message should go, so I debugged the value in the rule and it definitely should go to the when #2 but it just won't.  so did I do anything wrong or it is just the InterSystems doesn't like the iteration value here? I only need to evaluate the first pv1:3.1