The day after an event, someone asks for the report. A school head wants to know which parents came. A church board wants the offering and the headcount. A sponsor wants proof the room was actually full.
A useful report answers those questions without a second weekend of spreadsheet work.
Start with who was expected
Registration without attendance is a guest list. Attendance without registration is a guess. Put both on the first page, with the no-show count beside them.
Then add the times. A check-in curve tells you whether people arrived for the opening or drifted in after the keynote. That is more useful than a single total when you plan the next programme.
Keep the money in the same document
Ticket sales, donations against a campaign goal, and merch sold at the door should sit next to the headcount, not in three different apps. The person reading the report should not have to reconcile them.
Close with the list: names, contact details, and check-in status, exported so the next email, audit, or reunion does not start from a photograph of a paper sheet.
If you cannot produce that the same day, the system you used was only a sign-in tool. The report should be the event, written down.