What I expected to happen was...:
/effect <pseudo> <effect> 10 2 => give effect level 3
/effect <pseudo> <effect> 10 1 => give effect level 2
/effect <pseudo> <effect> 10 0 => give effect level 1
[...]

What actually happened was...:
Bug level

Steps to Reproduce:
1. Write command with effect as a level 2
2. View Inventory
3. The effect is at the level 3