The notifications page is where users can view notifications they're subscribed to and also subscribe to new notifications. The page is split into two, subscriptions via groups and your subscriptions.
Group subscriptions are listed at the top of the page and are set by the administrator via the Subscriptions page.. You can't delete group notifications but you can override them. Your subscriptions are listed under the "My Subscriptions" section. Adding a subscription follows the same steps as creating a group subscription which is outlined in the admin section.
Overriding Group Notifications
To override a group notification, you need to create a user subscription with the same Source and Publisher Type as the group notification. If there's a user and group subscription with the same source and publisher type, the group subscription is ignored and only the notification types selected (or not selected) in the user subscription will be taken into account.