Reminders
The first, second, and recurring reminders can be configured in the same way as the invitation, with the additional setting Notification schedule.
The first and second reminders can be sent on a 'Fixed date' or a 'Relative date', meaning the reminder will be sent after the configured time has passed once the activity becomes available to the user.
The recurring reminder allows you to send a notification at a configured interval after the activity becomes available to the user.