When you click on an assignment in the Assignment tab, you are able to view data for that assignment. When you click on a student’s name, it allows you to see how much time a student spent on each question and whether or not they got the answer correct.
This student below, for example, spent 18 seconds on the question “Reasons for line”. However, if this student worked on this question, didn’t submit his/her answer, answered a different question, and then returned back to this question, his time would reset. Therefore, the duration only shows the most recent time a student spent on the question, not necessarily the entire time.