Your descriptions are correct. The missing numbers are the UVW - unloaded vehicle weight (empty RV with full tank of fuel) and OCCC - occupant/cargo carry capacity...see:
http://www.rvsafety.com/weighing/weighing-glossary
The way it stacks up is:
UVW = Empty RV..
Add cargo (including the tankage) and passengers to not exceed GVWR (load allowed riding on the RV's tires)...this is called OCCC.
Add trailer to not exceed GCWR (total mass being pulled by the RV's engine).
When these RV's get this big, how much you load the RV (amount of OCCC used) will impact how much you can tow...up to the max hitch capacity of 5000lb.
Having said all that...there is probably plenty of carry capacity in the RV for the average owner
Hope that makes sense.
Best luck