Technically its not "out of" because in the linked article: "Hunter ID number (a number which I could validate but not easily trace to a particular person)" I

Technically its not "out of" because in the linked article: "Hunter ID number (a number which I could validate but not easily trace to a particular person)" I'd read that as some minimal formatting and the correct number of digits and you're in. I suspect there were no small number of school admins, teachers, parents, ex students, middle/grade school students, outright adult pedos, etc. More like 500 registered users out of a billion internet users.