"Missing" status stays after grade entered

Community Novice

Why does an Exam stay in "missing" status after I input a grade. Shouldn't it automatically switch to "none"? Other columns (discussion boards, etc.) do but not the Exam. I have to go into each student's grade and change the status to "none" in every class (about 400 students). Maybe it's because the grade was or wasn't entered in Speed Grader and the others were done the opposite way? It's very annoying.