Before starting, I want to say that congratulations on your mod and page (and editor). Really helpful.

Now, ,the thing is that I have JustHammers installed and I realize it does not count when mining with the hammer. For example, one hammer mines a 3x3x1 surface, so it should (for example) gives 9 xp for the mining category. But it didn't count any. Is there a way to solve this?

Edit: playing on minecraft 1.21

This is a known issue and there is no solution yet. Maybe try using a different hammer mod.