For most filters, these filter parameters and their widgets are defaulted with no values. For instances where a filter is developed that desires default AA's, AM's, or DC's to be prepopulated into that filter parameter, there are two lists that can be chosen: the "available" list widget, or the "chosen" list widget.
This seems mostly a design decision to me with little to no practical bearing. But it might bear a small discussion to settle on a standard for these filter parameters and their widgets.