A revision tag identifies the revision assigned to each cloud in a view. (You enter revision information on the Sheet Issues/Revisions dialog. See Entering Revision Information.)
To tag revision clouds
A project created using the default project template includes the Revision Tag or M_Revision Tag family. To check whether another revision tag family is loaded, in the Project Browser, under FamiliesAnnotation Symbols, look for the revision tag family name. To load a revision tag family, see Loading Families for instructions.
As you select each cloud, Revit displays a revision tag next to it. Numbers in the tags reflect the revisions assigned to the clouds. (See Assigning a Revision to a Revision Cloud.) On sheets, these tag numbers can differ. (See Revision Cloud Numbering by Project or by Sheet.)
You may need to zoom in to see the controls for the revision tag.
For more information about applying a tag to an element, see Tags.