Answer: "The tube comes with another part so that you can suction-mount it to the side of your bathtub, and you’ll have a bath toy for your kid. There’s also a ring that comes with the set, and it fits under the flared edge of the tube so that your kid can poor water in with a cup. The latter also comes with the set.

The numbers measure nothing, they are just here, so the kid can practice counting. The hole in the bottom allows water to drain out back into the bathtub."