Graph templates controls how your graphs look. By changing the template for on check command you can customize how the graph for that check will look.
By default a the template default is used for drawing graphs. This can be changed for a specific check command.
To change the template for a check command go to configuration and select graph templates. Select a template that you would like to modify, then press go.
Select the check command that will use this temple and select the template. There are several templates in the system by default.