Go to the GRADES tab in Moodle

Then Select SETUP from the Grader Report

Then select EDIT under the ACTIONS cloumn of the Course Folder

.Select EDIT SETTINGS and scroll to the item: Grade Display Type - Here you can select how you want the grades to display in the gradebook.  You can choose from LETTER, PERCENTAGE, or REAL -- or a combo.  Once selected scroll to the bottom to press SAVE to make the changes.