How do you make an ammo system

Help Requests
1

In my game Response Team, I’m trying to create an ammo system. For example, it starts with 64 ammo, when you shoot it it loses one, and you can collect ammo.

2

http://flowlab.io/html5/bin/1278662

3

https://flowlab.io/game/play/1271509
Iv’e made fully working guns, use my system instead