How the list of application with tray icons is created

Question

1. There is C# application with trayIcon.

2. In the windows settings the mode "show icon and notification" is set.

3. Application is restarted ->

   3.1 The new instance icon is hiden.

   3.2 The setup window contains 2 items of my app and the new has setup "show notification only"

The questions:

a) how this list is formed?

b) Where I am wrong?