What setMagazineAmmo would do:

The purpose of the command would be to remove ammo from a specified magazine class in the players inventory, examples of usage or syntax could be the following

primary/default syntax:
<object/unit> setMagazineAmmo [<classname of magazine>, <amount of ammo to set>];

This above example would set the specified amount of ammo on a specified magazine class from the players inventory, it will default default behaviour would be setting only one of the magazines found in the players inventory, if amount to set exceeds what the magazine can contain/has left in it the command will fall-back to setting the magazine to full or empty accordingly.

optional syntax:
<object/unit> setMagazineAmmo [<classname of magazine>, <amount of ammo to set>, <whether to remove the magazine if its empty or not>];