Sadly that's already been established! LOL I think they bought them because they hold more pee and she doesn't have to be changed as often or something. That seems more likely than mom just happened to accidentally buy size 6 twice! Once I could see and I would have tuned around and returned them ASAP, but twice?? No way! He always makes up excuses (cough cough.. Lies...) but this is a new weird one!