It's confusing, but it has to do with the fact that a certain percentage of students admitted will decline the offer of admission (to go to another program, continue to work, etc.) Not sure about SFS specifically, but I think the top IR schools (Fletcher, SAIS, SIPA, G-town SFS, etc.) admit around a third of those who apply and then about a third of those admitted will eventually enroll. That's how you go from 1000ish applications, to 250ish admitted, to 90ish enrolled.