This is one of the reasons that Bowtech typically posts a range of speed ratings for any given bow as opposed to just one flat speed. Productions tolerances vary some I am sure. Your bow may be faster because of the limbs, string construction, etc... It could be a variety of issues.

My Old Glory....at 60 pounds and a 31 inch draw with a 370 grain arrow was pushing 286 fps when I chronoed it last spring. It was pushing a 440 grain arrow at the same speed with the bow set at a 70 pound draw weight.