Sometimes you may need to see Default subscriptions for any user or group as there may be cases where they might be receiving notification twice for a single work item update or build update
Step 1: Go to Organization Settings
Step 2: Click on Global Notifications
Step 3: Click on Subscribers
Step 4: Then search for the user or group as shown below
Step 5: You will be able to see the list of Global subscriptions as well as project subscriptions in Azure DevOps for the user or the group