By default, data from Event Service Times is not included in your dashboard or regular reports, and so will not be included in any of those calculations for overall attendance.
If, however, you would like the data from a particular Event Service time to be included, you can do that by checking the Include in regular reports option.
It is important to check that box immediately when you create the Event Service Time, before you input any data for it. If that option is turned on after saving data, then it won't have any effect and the saved data won't show up on the dashboard or in regular reports.
This is because when you save entries on the input screen, it copies the option Include in regular reports to the records. Changing the service definition after the fact, doesn't update the records.
Fortunately, the solution is easy:
Make sure the Include in regular reports option is on (or off) as desired for the event service time.
On the Input screen, find the Event entry.
Make a small, easily noticeable change too all of the saved numbers - e.g. add "999" in front. Save the new numbers. Then, change them back to the original entries and click Save again. This will force the system to update the records with the new "include in regular reports" option attached to them.