Many, many games have multiple item numbers. Because of that situation, we only put 1 into the item number field and not all of them. And we try to figure out what the best number to use is.
Typically, this is a number on the spine. If not there, then on the back, if none there then on the media itself.
For Nintendo games, the number should be what is on the box. In the instance where there are multiple numbers on the box, use the one that has the country code in it. For example, Japanese *DS games have the item number with JPN in it on the front, rather than the back. For boxed Nintendo games, do not use the item number that is hidden in flaps, such as with SNES or N64 games, but this number can be put into description.
When it comes to PS4 games, the Style Guide was ammended to put a PS4 example in, to get people to put that CUSA number in. However, we are still using spine numbers for PS4 games. If the CUSA number is there, we will use that. If it is not there, you can put in that other number. Then you can put the typical CUSA number that is on the disc into description as "disc item number" ... and if the game has a third item number on the spine, such as Limited Run, it as well as the number by the UPC into description as well.
Examples:
https://vgcollect.com/item/130820The purpose of writing it out in the description like this, is so that if/when we ever update the site to allow us to add multiple item numbers, the information is already present on the entry, with a brief description as to where they are. It would make it a lot easier to update entries in the future, should it come to that.
And the reason for why not to put the CUSA number from the disc into the item number field is that you cannot make a proper first-hand identification of a sealed game, or from a photo or scan of an online sample, using the number on the disc because you can't see it.
PS: that string of numbers on PS4 games is also present on many PS3 and some PS2 games also, but I do not know if/how they correlate.