When I attended their mini open house, the dean shared that they are so committed to admitting only the best students that they have never accepted more than their maximum class size, even knowing that inevitably there will be people who would withdraw their offer and they won't fill up the incoming class. (Which makes you ponder when you consider that they do waitlist people, and since the purpose of a waitlist is for a school to have "back-up" students in case they don't fill up the class, doesn't this mean that pretty much all the waitlisted students at Duke-NUS will eventually get accepted?) So I wouldn't worry too much about the lack of spots.
Anyway, like they said in their FAQ, all applicants will be updated of their status by April. So all of us remaining applicants who are still "under review" just need to hang in there for a few more days!