Pie Chart- Static Data?

The pie chart represents that categories for the attendees. It looks like you have configured the site so that only the host can assign categories to attendees, rather than allowing them to assign themselves categories when they sign up. As a result, many attendees don't have categories set.

You can change this settings through the "Add-Ons" option under the host tools so that future attendees will have the option of assigning themselves categories, and you can assign existing attendees to a category using the Manage Attendees option, selecting sets of attendees and clicking edit.