How do I make an ammo counter

I want to make an ammo counter in my game I believe the best best choice would be to use a global variable. Does anyone know a better way? The global variable works fine. I'm just curious.

You could also use an instance variable if you wanted your ammo count tied to the object on screen. So if the object on screen is destroyed and you spawn a new one it will will start with the default value of your instance variable instead of needing to reset your global variable.

https://www.scirra.com/manual/73/instance-variables