Not really sure. I was told after everything, you are given a score... and if this score is between 2 set of numbers then you're waitlisted....
so I.E.
you get a score of 90 (after application & interview & whatever high priced donation you might make to HSDM for a new building to be named after you)
so say they say all applicants who score between a 93-88 are put on the waitlist.
KEEP IN MIND THESE ARE JUST RANDOM NUMBERS, I REALLY HAVE NO IDEA what 'actual' numbers they use.