As others have mentioned, advertised hitch weight is rarely close to what your real weight is. It actually goes up, before it gets off the dealers lot.
Also, keep in mind, hitch weight is NOT a constant number. It goes up and down during every trip, and it can be significantly impacted by the location of the holding tanks. Holding tanks that are located behind the trailer axles, will take weight off the hitch, and tanks located in front of the axles will add hitch weight.
My trailer has the fresh tank in the rear, black / grey tanks directly over the axles, and a galley tank up front. During any given trip, my hitch weight can be anywhere between 975 and 1225 lbs. The advertised hitch weight was 880 lbs.