In order to send a push notification, the user needs the Send messages permission. Check Permissions for more about the permission system.
After sending, you are redirected to the push notifications list where you can track delivery progress. The status column shows how many notifications have been delivered out of the total. Once all notifications are delivered, the status changes to Sent with a timestamp.
Note: Push notifications are only delivered to pass holders who have added the pass to their phone's wallet. Pass holders who haven't added the pass will not receive the notification.
Note: Google Wallet limits notifications to 3 per pass within a 24-hour period. Notifications beyond this limit will not be delivered until the next day.