The Notifications tab contains information about:
All available System Events
All project actors
Notification Matrix
View by Events
View by Actors
Notification Overview
This sections shows:
The assigned Notification Scheme
Actors (number of roles which used in the notification scheme)
Events in the system
Notification Matrix
This sections shows:
All available System Events as rows
All available Actors (Users, Groups, Project Roles, etc...) as columns
Notification Matrix which displays
 when an Actor notified for an Event on this project
View by Events
This sections shows:
Every Event as a row
Recipiets in the 2nd column, who will be notified
View by Actors
This sections shows:
Every Actor as a row
The Events when they get notifiend in the 2nd column