Aztek airbrush question

As far as I remember, those were the first cups, before the white models which are one piece only; you'll notice that paint gets out of the bottom of the white cup; let's say it's gravity feed; the grey and black cups work differently : paint goes outside the inside cup into a thin "tunnel" along the outside cup and into the outgoing tube to the airbrush; I should call it semi-aspiration feed; I don't remember of these cups being better or worse than the white ones; maybe they were intended to regulate paint flow, but I never saw big difference; apart from the extra cleaning, which is very little, you can use them with confidence.

I think you have the cup upside down. The black section is a top for the cup to help prevent spills when using. The bottom slot fits into the AB, and the air supply is through the AB, not the cup.