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You do have one interviewer. Mine lasted somewhere between 30 and 45 minutes (sorry, it was awhile ago). It might have gone longer, but my interviewer was a clinician and seemed extremely busy (had to wait for some time while he finished some work, then someone came in and told him he was "needed" as soon as possible, which ended our conversation). I would expect anything from 30 minutes to an hour, depending on your interviewer.
I'm pretty sure that he had read my file, but not sure about the secondary (not brought up, but there wasn't anything too exciting on mine).
I had my interview a week and a half ago. It lasted about 45 minutes. The interviewer did have access to my AMCAS app but said she did not look at it because she claimed the format was hard to follow. Overall it was a very informal and relaxed interview.