Left row, top to bottom:
1. in-game time when the last round is fired
2. whether the gun is chambered or not, 1 = chambered, -1 = not chambered
3. times the guns are cycled, which is equivalent of ammo fired by any one of the guns

Right row, top to bottom:
1. time remaining for the autoloader to be fully loaded
2. whether there's a shell in the breech ready to fire
3. total number of shells fired
4. number of shells in the autoloader

FireGuns: fire guns, the ammo-counting is automatic

FireWeapons: fire cannons, the cannons fire rapidly but if you fire all six shots at once, the cannon would now have a ROF of 1 shot/sec until the autoloader is allowed to replenish.