The DND (Do Not Disturb) mode allows you to deactivate the notifications for a set period of time (30 minutes, 1 hour, 2 hours etc. to up to 24 hours) OR until you decide to turn DND off again.
When DND is activated, you do not receive notifications. The app does continue to detect and record motion and to update your Event History.
The setting is listed under the Application Settings and applies to all the cameras linked to your Hubble Connected account.