Grades Start at 0 Instead of 100%. How do i change this?

Community Novice

All students grades started off at 0%. Once they started to submit assignments (on-time), their percentages started to increase. I need to input mid-semester grades, however I cannot provide the most accurate grade based on the assignments that have been submitted. How can I change the grading scale to start at 100 so I can provide students with their true grade?