Wait. . . Adjutant is a title, not a rank. What's my rank?
In a large military organization, there would be a full Adjutants' Corps, and their ranks would determine their various responsibilities, pay grades, and pecking order.
We're not a large organization. You're the only Adjutant, so the Captain made it a rank unto itself.
Then I'm unique here at the bottom of the org chart.
Ah, the burden of irresponsibility.