When multiple attempts are allowed, there are different ways you can use the grades to calculate the student's final grade for the quiz.
Highest gradeThe final grade is the highest (best) grade in any attempt.
Average gradeThe final grade is the average (simple mean) grade of all attempts.
First gradeThe final grade is the grade gained on the first attempt (other attempts are ignored).
Last gradeThe final grade is the grade gained on the most recent attempt only.