finished delivery alert

Hi Community,

need some help, I have set up finished delivery alerts for our instances, what I have noticed that even though the monitoring period is set to 24hours, the first email notification that is sent out via my dashboard includes a consolidated list of deliveries, i see deliveries dating back to 2020 as well.

example, email notification sent on 6/6/2021 at 12:02:00 AM

while, I feel this is a default behaviour in ACS, I wanted to double check, also if this indeed a default behavior where the first notification includes a consolidated list of all finished deliveries, 

Is there a cutoff point so that the consolidated message list doesn’t keep growing?