As seen from the screenshot, extension 2a of use case 3 indicates that if the list does not contain the person, it will show an error message. However, listing persons would only serve to list all persons in the addressbook and will not go any further to display any error message or find a particular person. At the stage of listing the persons, the system would still not know who the user wishes to edit. The system would only know after the user inputs the edit command with the index, which is covered in extension 3a.
As seen from the screenshot, extension 2a of use case 3 indicates that if the list does not contain the person, it will show an error message. However, listing persons would only serve to list all persons in the addressbook and will not go any further to display any error message or find a particular person. At the stage of listing the persons, the system would still not know who the user wishes to edit. The system would only know after the user inputs the edit command with the index, which is covered in extension 3a.