Arbortext IsoDraw > User's Reference > Menus > Window Menu > Show Attribute Window > Renumber Callouts
  
Renumber Callouts
 
Selecting this command updates the numbering. If you have deleted one or more callouts, gaps will have appeared in the ascending numbering. The update closes these gaps. For instance, if you have created eight callouts with the numbers 1 to 8 and then deleted callout 5, the subsequent callouts (6, 7, 8) will be moved down one number; i.e., to 5, 6, 7.