Well then, you have confirmed you have a few screws loose... quite a few in fact.
I have replaced a vent before and found a boatload of screws as well, but probably only 16. I guess they want to make sure that vent stays in place, especially if someone puts some kind of vent cover and attaches it to the vent. I have done this as well and the cover only needed 4 screws and 4 sets of nuts/washers/brackets. 31 screws sounds like overkill, but maybe they found something and decided it was better to just double the screws. Now that you fixed it, you probably lessened your rig by a few ounces (unless you put the leftovers in the RV somewhere).
