I think that you are mixing apples and organges. Look at
this website for some clarification.
Forget about the towing deal for a second.
I looked at the spec for your vehicle. It says that the GVWR is 6500 pounds. That is the total max weigh that the vehicle is rated for. which includes a dry vehicle weight of 4545 pounds, a full tank of gas and fluids, and 1050 pounds of passengers and cargo. This will include the tougne weight of a trailer. So if you can carry 1050 pounds of cargo and people and your tongue weight us 620 the numbers are 1050-620 = 430 pounds of cargo and passengers in the jeep.
You can distribute this as your see fit as long as you don't put any more weight on the front axle than 3200 pounds or 3700 pounds on the rear axle.
How to get to the towing capacity. According to the specs you can tow a trailer that weighs 6200 pounds with a tongue weight of 620 pounds. The tongue weigh would have to be figured into your GWAR on the read axle.
Finally you will need to check the hitch rating . The hitch that is installed on your Jeep will determine the maximum weight of a trailer that you can tow. A class III hitch is rated for a maximum weight of 6000 pounds. I would bet that you have a Class II or III on your jeep. I will let you look up hitch ratings
here