The three types of data callouts.
Data callouts give imported data real visual payoff. When you create a new data graphic, you should customize its callouts so that they show just what you want them to show.
Visio gives you three types of callouts:

Text callouts.

Data bar callouts.

Icons.
The server shape in the picture has all three types in its data graphic. This lesson will go into detail about each type and how to work with each.