There are multiple types of grading that can be applied to each activity for each student.

1. Empty Grade

Indicates a missing grade. Grades can be empty if the assignment is not yet graded or if the quiz is not yet attempted. Not be confused with 0, empty grades might be ignored by Moodle LMS if the category settings are not configured correctly. This calculation behavior might cause unintended effects on the category total grade for students. Consider the following scenario:

Both students have equal grades for all quizzes except for the fact that Student A missed Quiz 1. Still, because of the calculation method (Simple Weighted Mean) and the fact that empty grades are excluded, Student A scored similarly to Student B as the system ignored Quiz 1 all together and did the calculation as if the Quizzes Category contains 3 Quizzes only, which is not true.

To fix this error, we include empty grades (unchecking the option as shown in the screenshot). The calculation will more accurately reflect the students' grades:

If you would like to keep the option checked, you will need to manually override all empty grades and set them to 0.

2. Obtained Grade

This is a grade obtained by the student. If the student attempts the quiz or if an assignment is graded, then the grade will show without highlighting.

3. Overridden Grade

This is a grade that have been assigned manually by the teacher, overriding the original grade of the student. Overridden grades will have their cells highlighted in a yellow color.

Next, let us demonstrate how to override empty grades for all students in case you would like to keep the option "Exclude Empty Grades" checked.