For Non-Edi Qualifications, you'll need to select an aspect gradeset in order to manually add results. If an incorrect grade has been selected by mistake and marks have been entered you'll first need to remove these marks before you can edit the gradeset.
To do this go to Students > Examinations > Results Administration > Non-EDI Manual Entry and select the Non-EDI exam.
Click on the grade and change this to No grade.
Once all marks grades have been changed to No grade click on the current gradeset under Aspects.
Click on Edit and Delete the current incorrect gradeset.
Once deleted use the +Add button to select the correct gradeset.
You can now re-enter any marks with the correct gradeset.