You can change assignment grades in the gradebook's Student Results Summary but not grades for
You can also change any grade you entered in a manual column in the Student Results Summary.
To change a grade:
The changed grade is displayed with an asterisk, for example, 80* or 80/100*.
To reset the changed grade back to the original grade, repeat steps 1 through 4 and, for step 5, click the Reset button.
See also:
Grades as points or percentages | Reset exercise scores