Configuring Default Notification Settings for Users

In the screenshot that you shared, all of the notification levels start out with an empty list of tracked categories or tags. Does this mean that by default, new users enter into a Discourse forum without any notifications for any categories or tags? I don’t think this is correct, but maybe it is; if users do have some default tracked categories or tags, then I want to understand how that functionality works and how it intersects with these settings.