Yeah, I made that code, and I wouldn't use it except to play around. The inventory system in this game was kind of goofy, and hard to edit directly with cheats. I actually had to use the game's inventory functions to add selected items, and the "all items" cheat just iterates through the available values with no regard for whether or not having the item, or 99 of the item is advisable. I hadn't even completed the game when I made it, and didn't even know what half the stuff was.
Editing this line: 200C0500 24120063 will change the quantity you get. It's at 99 there, and changing the last four positions will alter it. So 2412000F will get you 15, or 24120009 will get you 9. However, I'd just all around advise using the "have items" code and just hacking in specifically what you need with the quantities you want. 90% of the items are junk (if you're cheating), purchasable with infinite cash, or they're things you only need one or two of, even excluding the story items.
If anybody wants to compile a list of things that ought to be excluded, I might be able to change the "Have All Items" code. However, as I recall, there were just too many things to exclude, scattered all through the list of available items.