Offline alerts audit is available under the activity tab in the diagnostic and shows the current grade from the data obtained yesterday and a small historical chart for the performance of the last week. The grade is determined depending on how many offline alerts you got. The more alerts per worker, the lower the grade.
Alerts are one of the mechanisms that are helping you to keep your mining operation in good health. However, receiving too many alerts just isn't efficient. You probably won't even read them since there are too many of them and it will be very hard to examine your 24h activity log. This is why it is OK to receive some alerts, but not too many of them.
Getting a lot of offline alerts in one day usually means that the worker was coming and going online and offline.
If you want to improve your offline alerts grade, try to: