Cheers, and good call regarding the non-game-breaking bugs.
To fix the ammo counter display is actually not hard in theory, all you have to do is, once you've updated the internal ammo count, you update the actual label only if the ammo type you picked up is equal to the ammo type used by the weapon you're holding. In practice, I'm not sure exactly what you would need in your case since my own code is very different from the course. You may have to tweak exactly what's available in the WeaponManager, etc., but that's how you would go about it.