This is the part most reports skip, because most teams have nothing to put in it. A survey tells you how people remember the session. This section tells the reader what the room did while it happened.
Fill it in part by part, using the published agenda. For each part, write how much of the room faced the front, as a likely range, and how many people were in view. If the footage of a part is too thin to read, write "not measured" and the reason. A blank you explain is worth more than a number you guessed.
You can fill it by hand from notes a staff member keeps at the back of the room. Or Proof of Impact by GRW can fill it from the video you already record. It reads the audience as one group, never one person, and gives a part a range only when there are at least four people and about a minute of steady view.
One session, one report, $499 CAD. No subscription.