You are correct that a formal way of saying, "What did you say, Mara?" would be "nuq Dajatlh, mara?" However, if you look up "nuqjatlh" in the dictionary portion of the addendum (page 183), you will see that it is an exclamation meaning, "what did you say? huh? what?". Since students are still learning the grammar at this point, we have decided to introduce them to this useful exclamation early in the course.