There's a sending unit in the fuel tank. It's variable resistor connected to a float (not unlike a toilet bowl float). it will read something like 20-150 Ohms. If Jeep's system gets an erroneous value, the system defaults to displaying an empty tank. Overfillling can cause this problem. Perhaps it got stuck or broken. Also, a slight adjustment error during assembly can cause this problem. There's a chance as you burn down about 1/2 your tank it will reset. I worked with one of these systems interfacing a generic sending unit in a fuel cell for a driveline transplant. I solved it by inerting a 10 ohm resistor inline, but that's too much info.
If it doesn't fix itself at 1/2 tank you are going to the dealer. They will read the code, likely reading a malfunction and then probably drop the tank and replace the sending unit (might include a new fuel pump).
They would appreciate it if you don't take it in on a full tank.