You have an airfield group selected. Thats the symbol for that. If there is a bunker as part of the airfield, you'll have to use the unit view to see it. Is that the issue?
The installer will delete your Command.ini config file, which means the game will use the default settings. One of the default settings is to use NTDS/APP-6 icons for units. You can change this back to "Stylized" or "Directional" through the game options.