Grades may be displayed as as actual grades, as percentages (in reference to the minimum and maximum grades) or as letters.
To change how grades are displayed for particular grade items, or category and course summaries (called aggregations):
Click Grades from the Navigation Menu.
Select Setup from the top row of tabs.
Click the Edit then edit settings link opposite the grade item or category total. (For the course total, click the Edit then Edit settings link at the top of the actions column, opposite the name of the course).
On the edit category page, click the Show more... link under Category total.
From the Grade display type menu, select real (for actual grades), percentage, or letter.
Click the Save changes button at the bottom of the page.