towing a 850lb pop up camper with 2004 Toyota Matrix xrs-6 speed manual?

The total weight allowed is 1500lbs for this car..I towed it on flat valley land-piece of cake..Now, I am going up to Yosemite and mountains..I just saw on the door that total weight: cargo and passengers is 860lbs. I will have myself (120lbs) and 2 poodles (28lbs total), cold box/dry food etc. I'll buy water at the valley store to keep weight down. Will I be ok? I just wonder why the manual says 1500lbs total weight for passengers, cargo etc. and, then on the door it says 860lbs? This is a vintage Coleman 1980 or so Jamestown one-wing pop-up camper-7ft square box...what do you think? I still have not mastered back up..alas!