To add footers, click the "Display Options" button at the top left of the Gradebook, and then click "Visible Footers..."
Select the footers that you would like to appear in the Gradebook. The options are "Missing," "Score Entry," "Points," "Low scores," and "Category." When selected, click the "OK" button. The "Missing" footer tells an instructor how many students have NOT provided a submission for the assignment. The "Low scores" footer tells an instructor which students do not have a passing grade for the assignment. The "Score entry" footer tells an instructor the method by which the assignment was graded. The "Category" footer tells an instructor the weight of the assignment within the category.
NOTE: If you ever forget what a particular footer indicates, hover your mouse over the title of the footer. A description will appear.