Is this guy absolutely certain the gauge showed 2% and not 20%? At 20% that 50 gallon fill is only 6 gallons off. I seriously doubt the dealer gave him his boat with 1.4 gallons in it, at 20% that would be 14 gallons in the tank. And if he tried to fill the tank at max flow it could have easily not taken that last 6 gallons.
There is a small flapper valve in the fuel fill line down close to the tank, this flapper is designed to keep the fuel fill tube full of gas so all of the air / vapor in the tank is forced out through the carbon canister, several people have had issues with this valve being in the line crooked, don’t assume yours or neighbors is, it’s not common. In practice, if the tank is low you can go with a higher rate of fuel fill until it clicks off the first time, then go with the slowest fill rate to finish filling the tank. Others have had issues with the carbon canister becoming full of fuel (from repeated topping off attempts) and not venting correctly, others have found theirs with water in it and not venting properly.
On your connext screen on the tab that may look like a flattened U shape, there is a fuel used line, that has proven to be far more accurate among this group than the percentage gauge, mine is accurate to 1/10th of a gallon. Be sure and reset this page to all zero’s.
What does your fuel gauge show currently?
I realize your boat is new, but, when you fill your boat up, use the slowest setting on the fill handle and don’t try and top it off by repeatedly squeezing the gas pump handle, you will hear the fuel come up in the fill tube, try it once more and if the fuel comes right up you’re done. Once that is done get in the boat and turn the batteries on and check the percentage gauge and it should read full.