Payload is how much weight you can add to the suburban itself.
Fuel, passengers, any other load, suitcase, dog food, whatever, including the tongue weight of the trailer. All of this must add up to less than the 'burb's GVWR.
The other really important # is GCWR, gross combined weight rating. IF you start with the burbs GCWR from the tag on the doorjamb or the owners manual, subtract the actual weight of the vehicle and everything in it (above) what is left is the max weight your fully loaded trailer can be.