the "N" in "nth" is a number variable.
to say "nth element" is to say "any element that's in the index N".
N also means the number of items in a set. So if I have 10 instances of Object, N=10.
like TELLES0808 reply, it could mean the last item (since N literally is the number of items), but it could also mean "any number between 0 and N" (like in our case).