I would be very surprised if the actual weight was even close to the GVWR. My 14,000lb loaded Jayco weighs 11,500 at the scales with a 2600lb tongue. You are doing the right thing taking it to the scales, I think you will be happy with the results. Maybe an engineer can explain why axle weights and GVWR don't add up, but I've never found anybody that could. Somebody mentioned tires as the limiting factor, and they are. However, on a dually you are going to have about 12,500lbs of carrying capacity and tongue weight is subtracted from actual weight to get your sprung weight. You'll be well within limits there.