There's an air valve in the end of the nozzle that shuts off the pump if the tip gets submerged. Stay on the bike, lower the tip into the tank to the desired fill level and hold it there with both hands. It will shut off automatically when the fuel fills enough to reach the tip.
Be careful not to scratch the inside of your tank with the metal nozzle - it has a special protective coating.
Your gas tank is directly over a big hot oven so the fluid will expand as it warms. Quite a bit, actually. If you fill to the brim, fuel may start squirting out everywhere after a few minutes and soak your bike from the top down. You may even have time to pay and resume driving before it starts coming out your keyhole. This is dangerous.
When I first learned this, my bike had wet itself and stunk of gasoline so I studied it instead of resuming my journey. I eventually figured out why my engine was drenched in gasoline roughly around the time the bike had dried off which took quite a few minutes. Don't overfill your tank.
On the other hand, if you ever wanted to pilot a fireball, now you know how.
