How to generate a report on Group Administration?
Perform the following steps to generate a report from Group Administration events:
When you click on any one of the recent events based reports, a dialog will appear as shown below, for user selection, whose events you would like to see in the generated report

If you would like to view events for a specific user, select the "Specific users" option, and select the list of users by clicking on the "Select users" button

For Top users based report, a dialog will appear as shown below for selecting events and date range for fetching the list of top users who had performed the group administration events recently
Once you click on "OK", the report will be generated as shown below,

In the above screnshot, the "Operations" column will show the event type that occurred, "Event Date" and "Event Time" columns will show the time when the event occurred, "User Id" column will show the user who performed the event and "Event Details" column will show other related information like Site URL, File location etc.
You can select the "Summary" option in the Report view section, to view the summarised data of the events that occurred in your tenant recently. There will be options available to summarize data by "Daily", "Hour of the Day" and "Day of Week". This summarize window will be displayed as shown below,