This isn't your dad's punching bag as the bag punches back if you don't compare numbers correctly or take too much time.  If the bag lands a punch then you lose a life and you're that much closer to getting knocked out!  Simple to play just look at both numbers and tap on the correct sign:  "<", ">" or "=".  As you box more you'll have less time to throw punches before the bag punches back and the numbers get larger!