Why this clause is dependent?

While preparing for my SAT, I encountered the following sentence:
"According to a survey analysis, veterans returning to the University of Illinois had 6 one “predominating request”: an efficient course of study to prepare for a job."

There is the colon between two parts of the sentence, as you can see. It seemed for me that there should be semi-colon, because I thought the second part of the sentence ("an efficient…") is independent. However, correct answer is putting colon, and explanation says that the second part of the sentence is dependent. So I did not understand why.

If we read that clause ("an efficient course of study to prepare for a job."), it looks fine on its own, isn’t it ?

Nevertheless, I can’t go against Khan Academy, so can someone explain me why the second part of the sentence is dependent ?