The none value in custom variable

I set up an eVar to capture the login status.  It includes the values no, yes, and facebook.  None wasn't a value we expected but Omniture is passing because it didn't have a value at the time the event was recorded.  That's fine.  The problem is when you add up all the permutations of the visits.  It goes over 100%.  According to client care, it's because the event is fired twice.  Once with when there was no value set and then again later when it is set.  So to clean it up and to have things match the 100% I adjusted the none visit percentage to be what's left over from the other three values.  Why can't Omniture update the logic and do this?  

Robert