gvwr 16,500lbs gcwr 21,000lbs weight 12,500lbs????
GVWR is the MAX motorhome can weigh (16,500)
GCWR is the MAX motorhome AND anything towed can weigh combined (21,000#)
The 12,500#...........if that the curb (dry) weight of motorhome you can load motorhome with 4000# of stuff before reaching GVWR (Fuel, water, propane, passengers, stuff/cargo, tongue weight of towed vehicle etc.
8500# of stuff in motorhome plus tow vehicle weight before reaching GCWR
BUT total weight of motorhome can not weigh more than GVWR
SO if motorhome is MAX'd out at 16,500# than towed vehicle can only weigh 4500# (GCVWR--21K)
Course you also need to be aware of RAWR and Tire Max Load Ratings..........don't exceed those ratings.