[playbox12]

Depends on how you use it your MAX_ITEMS define, it's just a command to the pre compiler so the former gets replaced with the latter during compiling* (MAX_ITEMS will be replaced with whatever you put to the right 'MAX_ITEMS 50' will replace MAX_ITEMS with 50 everywhere in your script).

If you use it to define an array it'll make the array 50 slots big, that's all it does really, just simplifying your needs.

*Or actually just before it starts compiling, pre check.