I interviewed in December and got accepted a few days after. To answer your question, when I interviewed, there were approximately 50 students online. In order to be able to interview everyone, the staff organized students in 3 Groups -- A, B, C. These are not room assignments, they are just chronological groupings to determine who interviews when. While one group is interviewing, the other groups are listening to presentations about student life and hearing from student-doctor ambassadors. Back to the question. The Groups are then further broken down into sets of 3 students and assigned to different zoom meeting rooms. You don't have to worry about groupings/room assignments, they take care of all of this for you.
The interview is both structured and conversational. It is a laid back interview with no "gotcha questions", but I would still prepare answers for the common questions on the school's SDN interview page. My interviewers asked each of us questions -- so there is no need to be nervous about not being able to get some words in, they will make sure to call on everyone the same number of times. If you have any more questions, don't hesitate to ask! You're gonna do great, and of course, be sure to send the interviewers a thank you email after the interview.