Heartland states that the empty weight on a 2008 Bighorn 3370RL is 10,635lbs and the Hitch weight is 2,065lbs, but when I weighed the empty unit on a scale the actual empty weight was 12,300lbs? and the hitch weight was 2100lbs. There was no water in the tanks only 60lbs of propane, no food or anything, we just purchased the unit. Why is there such a difference in weight?