This error arises when there are two, or more, entries for the same class name in the Class Information area on the front page of the Spring Census. Return to this area and click on Class Details:
Check the class names are correct. If you need to edit a class name, click on the pencil icon in the Actions column. To delete an entry, click on the dustbin icon.
Save your changes by clicking on the tick icon in the Actions column, then recalculate the census.
