I thought it was obvious that it came from Honda. It's mentioned several times at the Honda site.
Also, how much fuel fits in the tank varies quite a bit depending on how you fill it.
IIRC, if you slow fill it, which takes 16hrs from empty or overnight after 100 miles of driving, you get the most fuel in. If you fast fill it, you get less fuel in due to a "fast fill effect", whatever that is exactly. It has something to do with the pressure and temperature of the gas.
The warmer the fuel, the less will fit in the tank because it expands, and when you compress the fuel, it gets warmer, etc.