Right, it allows you to connect an aftermarket (not OEM) Alpine changer and an aux input. The one without the "D" is to only add an aux input, but no changer.
I'm in the same boat you are, where I have an OEM changer and Nav. As far as my research has discovered, it works with Nav, but our OEM changers don't work with it -- I remember even emailing Blitzsafe to double check. Kinda sucks.
Better picture coming!