There are several hybrids with ranges well over 500 miles per tank.
The Clarity already gets good gas mpg it would not take a much bigger tank to get impressive range. Even 1 gallon would make a difference.
In practical terms it is not an issue. Today I told the attendant that I just need a little top up even though the car had at less than half a tank. After the car took only 3.7 gallons the attendant said “oh, you were almost full already”. I just smiled.