Where did the tube blow? If it's at the valve stem seam, then it's probably just tube failure and not a pump problem. If elsewhere, then maybe if the tire is old, the bead became unseated or something. In any event, it's hard to tell but I doubt you overinflated it. Other reasons for misleading gauges has to do with how good of a seal you are getting on the valve. I think that the pumps that have 2 holes--one for schrader and one for presta tend to be less reliable because they may not seal as well on the side you're using. Or maybe the one I had like that just sucked. If you never really use the other type of valve, then there isn't much point in having a pump like that anyway.