Multiple out-of-date alerts after changing schedule

I have a query with the search's schedule, initially set to run hourly. 

Then I wanted to temporary disable alert and changed it to run daily. 

After some time I wanted to re-enable the alert and changed it to run hourly.

Then I unexpectedly receive several alerts within a few minutes for the time ranges in a past, when schedule was to run daily.
 

The same behaviour was noticed a few times with different queries.

 I also noticed that I received alerts for only some of time ranges. In particular I receive only 4 alerts, when the alert was disabled for more than 24 hours and threshold was exceeded all the time.   
The emails have different Time Ranges in a past but all were send approximately at the same time.

I would appreciate explanation why these alerts are send and advice is it possible to avoid them.

Regards,
Michael Freidgeim