The weight listed is notoriously low on Hi Los, but with that extra 400#, I'd kinda think the difference was between a Tow-Lite and a Classic, just my guess. I've looked at NADA charts very often and when a person asks for info from NADA, they really can't a true picture because NADA doesn't break it down to individual type units enough. Weight charts don't include added accessories , like full propane bottles, A/C unit etc. Truly, NADA info is just that INFO, and not to be held as truth. hope that helps.
Treeclimber