Moodle Quiz cutoff time

What does the cutoff time for a Moodle Quiz control?

The Cutoff time prevents both starting a quiz and submitting an already-started quiz once that time is past. Instructors can check the unsubmitted saved answers and the answers are checked against the correct answers, but no grade is given (it looks like instructors can’t manually override it) and students cannot check their answers. If the cutoff time comes while students are taking the quiz, a warning message appears and once the cutoff time has passed, they cannot submit their answers.