Adjusting Water Level in Toto Drake Bowl

first make sure the black rubber tube is pointed into the white overflow tube.
This is the "make up" water for the bowl.

The water in the bowl is determined by the upper curve of the trapway.
It acts like a dam. The water won't get higher than that.

1.6 gallon toilets do have less water than bowls for 3.5 and 5.0