1. A one-sentence summary of bug: 
The "next lvl:" count showing how many more mobs need to be shot to reach the next level is bugged.
2. Priority to fix? {High, Medium, Low}
Low. It does not affect the crossbow at all, just the count number is not accurate.
3. Which server? {Spawn, Redwood, Cypress, Maple, Willow, Expanse, DungeonRun, Rush, Creative}
All tree servers
4. Steps to Reproduce: Please list the step-by-step methods to reproduce the issue
Get a wilder crossbow, the next lvl count is right at first. Level it up once, then the count will start to go into the negatives and not update. 
5. Expected Outcome: What did you expect to happen?
I expected the count to update to show how many more mobs needed to be shot for the next level.
6. Actual Outcome: What happened instead?
It did not update, and it just started going into the negatives.
7. Proposed Fix (Optional): Do you have a suggestion?

8. Notes (Optional): Anything else we should keep in mind in relation to this issue?

9. Screenshots (Preferred): Do you have screenshots of the problem, proof or reference?