When choose from the list box the same Groups as the Inherit (In this case firstgroup). This monitored Item will not follow the Inherit System Escalation Groups,
The application will keep notify the only the firstgroup, even if you change the "Receive Notifications" as you have configured via the Groups Receives Notifications for this Agent you are working on. So if you change the Receive Notifications to Windows and Manager, the Notification Group for this item will look like:
In the Normal User Menu, you will see in the first total tables of monitored items also the selected Groups.