Revealing mistake: On night 21 the time-stamp changes from 11:59:56 PM to 11:59:57 AM despite it not having turned midnight yet.
Revealing mistake: In most of the shots with fast forwarding you can see that there is no synchronization between breathing movement of the stomach and the time passing by (most obvious on night #15 when Katie is standing looking at Micah who's still asleep). (00:37:50)
Answer: It's just a movie poster, not showing any part of a scene. Some movie posters may take different parts of the movie and combine them to make a more suspenseful image for the movie poster/teaser. There is a part in the movie with a shadow on the door, and there is a time where they are together on the bed in a similar position. Combine the two to make the poster interesting.