What has already been said, really. It's like the difference between ordinal and cardinal numbers. Also, if you're in a race and you overtake the person in 3rd, which position are you in?
Rydian said:
In some games the number displays your total lives, and in some it displays just your spare lives.
Like how your closet at any given day does not have all your clothes, because you're currently wearing a set.
3ds still seems to be an emulation powerhouse with little to counteract it (what are you going to use? A phone... hah). To that end second hand prices are likely to remain for a while