If you manually alter the final score on a quiz and then decide to clear that score, you can use the Recalculate option to automatically recalculate the final score. Refer to the following documentation to learn how to recalculate quiz grades.
Log into D2L and from the Assessments drop-down menu click on Quizzes.
From the drop-down menu next to the quiz click Grade. A list of all the students and their attempts will appear.
Click the Attempt 1 link below the student's name.
If you've already entered the scores for the essay, click the Recalculate button. It's to the right side of the page in the Grading Feedback section.
Click the Save button. The student's score will be updated.