Events. All events is the default. The menu does nothing until you press Apply.
Open Events. The menu says all events and the button is Apply. Example Co has four: disk_high on Accounts server, the external address change on that same machine, a reboot on Reception PC, and the hello from when Accounts server connected. Newest first. Changing the menu does not hide a row. Apply reloads the list.
Set the menu to disk_high and press Apply. The reboot, the address change, and the hello drop out. Accounts server's disk line stays. The count says 1. Set the menu back to all events and press Apply to see the other three again. Nothing is deleted.
The unfiltered list is Read the event stream. One machine, including a severity filter, is Read one machine's events and Show only warnings on one machine. The same menu for a sub-company user is Show only one kind of event on your machines.