If you shot it in after your last weight while tillering, then that may be what happened. Sometimes you lose weight shooting a bow in. Also, if you had a lot of sanding to do, like removing tool marks etc, then that will cut weight too. You can toast the belly if it ain’t backed, and that usually adds weight. It can change the tiller too though which will result in having to remove some more wood and maybe coming up at the same weight. If your regs say 40 lb minimum draw, I don’t think there will be a specified draw length. If you’re tillered to 30” mark that weight “ x weight @ 30” ”. If you’re 38 @ 28” you’ll be over 40 @ 30”