Edit - Delete - All Case Names

Ribbon bar. Select the Edit tab. In the Clipboard/Data group, click Delete and from the menu, select All Case Names...

Classic menus. From the Edit - Delete submenu, select All Case Names...

...to replace all of the existing case names of the spreadsheet with consecutive numeric values beginning with one (i.e. 1,2, 3, ...). This option is not available if the case names are currently labeled in this manner.