This option is a comma-separated list of numbers representing the days after a notification fires to send out a reminder. For example, 1,3,5 would fire a notification on day 1, day 3, and day 5 after it is triggered.
To enable this feature:
Click on the gear icon and select Settings.
Click Asset.
Select Additional Reminder Notification.
Enter the values, i.e. a comma-separated list of numbers to set the reminder notification.