The "What If" button on the screen lets you show a student how their grade would improve if they made up missing work, or how well they need to do on upcoming assignments to reach a certain grade. To see this hypothetical grade, change one or more of the student's scores, then click "What If". (The changed scores will not be saved unless you then click the "Save" button.)
Note: Click the "Hide Grades" link below the list of students so you can show a student their "What If" grade in your gradebook without them seeing other students' grades in the left column.
Video: Advanced Grading