When setting the level property of water using a /setblock command, I noticed there was a mismatch between the the level property I specified in the command and the level property reported by the F3 Menu.

I checked all possible level properties below 8, and they appear inverted
7 -> 1
6 -> 2
5 -> 3
4 is correct
3 -> 5
2 -> 5
1 -> 7