If I may. A real history and fictional lesson is in order.
This is just a commonwealth misconception about how ranks from wartime US Navy actually work. They are not the same obviously.
This is where the confusion starts to come into play. And why an (Acting) Ensign is not a Midshipman.
Now to clarify how the TSN works, looks at Star Trek please.
And all of that is based on this:
By the by, the title of Acting, came about from the (in)famous Wesley Crusher on TNG. Sadly it wasn’t really used since then on Trek. Odd. But it is a real thing.