No idea from the top of my head, but if you search the message it shows when it's full, or the limit amount (which could be 5000) - then you'll find it there.
However, if you mean it disconnects the user, then you would need to modify the SWF, as the emulator inventory isn't coded correctly (to handle XX amount).
You can modify the amount in their rooms easily I think?
But in their inventory the user will disconnect if they've got so many items. (When opened up)