I had the same question after driving away from the dealer's lot.I just purchased a 2018 Pilot Elite and only beginning to understand the 695 page Owners Manual! (WOW!)
I searched and found the Fuel Capacity is 19.5 gallons and the Dealer gave me a "full" tank.
The Range is reading 354 miles (?) The Owners Manual states that the Range is calculated based on the fuel economy of the most recent trips. (it had 100 miles on it and terrible gas mileage from short trips and idling).
What kind of Range can I expect? (hoping closer to the 450 mark) and can I reset this?
On my next gas refuel, the range jumped up to around 420 miles, so don't panic about the 354 you got.