macOS NSPopupButton's last item is a description of the selection set

hi all,

I have some popup buttons that are bounded to some array controllers

The Content is bounded to an Array Controller
The Controller key is set to arrangedObjects

Content Value is bounded to the same Array Controller
Controller key is set to arrangedObjects
ModalKeyPath is set to the property to be displayed

Selected Object is bounded to the same Array Controller
Controller key is set to selectionIndexes

When i run the program the bindings appear to work but the last menu item of the popup button is a description of the selection set...
any idea what's wrong or do i need to provide more details?

Selected Index is what i should be using and set Controller Key to selectionIndex
I'm sure i tired that before and it still didn't woirk.... oh well...