Product review (5 stars): Yes, your new belt is 1" shorter - but that's correct!
Your new belt will be 1" shorter than the one you're replacing.  Just give yourself access to the motor and drum and STRETCH that bad boy on there.  Trust me, it will work.  Just hold the belt on the drum and muscle the drum which ever direction your're feeding the belt.  You Tube will also show you.  It's easy.