ah, now i understand what you mean. i guess the person was referring to the items that are on your card not in your game ^^thank you very much!! now i can safely scan the card then dunno what happened with the person i read the problem from but just didn't wanna make the same mistake if anything.
like when you have 64 items saved on your card it will likely write the new ones over the last ones you saved before, but idk i never tried doing that. so if you wanna keep the items on your card, or plan to pass the card and content on, maybe just don't save new items on it, or make a new room that has both the old and new items in it and save that one on it.
anyway have fun with your new items