Defining default values for a certification type means that new certifications and background checks of the type you specify will be created with the values you enter here. For example, all new certifications of a certain type could be created with a status of Pending, or of Completed. Edit a certification's default values from within the certification's setup, by clicking on Edit default values.
What you'll see on screen looks very much like a certification or background check editor, with a few exceptions:
Edit the fields as appropriate. To remove all default values for this certification type, check the Delete all of these defaults values checkbox.
Changes made here do not affect any existing, saved certifications: only newly-created ones will appear with these values.