When you add any graded activity (such as an Assignment or Quiz) to a course, Moodle automatically adds a corresponding grade item (column) to the gradebook. You can also create grade items (columns) not linked to Moodle activities by adding them manually on the Grades > Setup page. 

1. From the navigation bar on the left of the screen, click on Grades
2. Once the Gradebook is up click on Setup

3. At the bottom of the page click on Add grade item

1. Name the grade item at the top of the page
   1. Show more… (ID number, Grade to pass, Grade display type, Overall decimal places, Hide and lock dates)

4. Set the Maximum grade
5. set the Minimum grade, in most cases this will be left at zero, this is not a grade to pass. 

Parent Category

1. Weight adjusted - uncheck this to reset a grade item weight to it automatically calculated value. Checking this will prevent the weight from automatically being adjusted. 
   1. Set the weight of the grade item here

7. Extra Credit - placing a check in the box will set the item to extra credit.