For more information about Grade Translations and Assessment Grade Plans, you can view this article about creating Assessment Grade Plans and this article about tying a Grade Translation to a Grade Plan.

To edit a Grade Translation
  1. Go to Academics
  2. Select  Grading > Grading Setup
  3. Select Grade Translations 
  4. Click Edit to the right of the Grade Plan
Note: Editing a Grade Translation will adjust the information historically if it has been used in past years.