By and large (no pun intended), that "cargo load" would have to include you, so, that would limit it to 750 lbs. Your cargo load would also have to include the weight of all the "options" that are on the trailer; i.e., battery, propane that's in the tanks, the awning, the microwave, etc., even the "mandatory options"...the dry weight of the trailer is for the "stripped to the bones" version.
All that being said, if you are right at the limit, and you really shouldn't routinely carry so much that your frame/suspension is "maxxed out", I would not worry too much about the adding of yourself to the load calculation. By and large, when you add yourself to the equation, you'll be parked in a campground or at home with the tongue jack down and the stabilizers set. These will help support any "overage" that adding your 250 lbs. might add to the total load. You definitely, though, should never be "over" when your trailer is set for on the road towing.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)