600th Floor

It didn't help that Leroy was team Jacob.

A security guard was sitting behind the desk in the lobby, reading a big black book with a flower on the cover...I said. "Six-hundredth floor.”..."There is no six-hundredth floor, kid."
~The Last Olympian

Look an allusion to Twilight.

Allusion to Harry Potter -->[link]

pointed this allusion out to me, I had missed it. It must be because I don't like twilight I must not have been paying close attention when I was reading.

Twilight (c) Meyer
Percy Jackson and the Olympians (c) Roirdan