You can zoom in to the data shown in a chart's viewport to decrease the time span that is displayed, and you can zoom out to increase the time span. By default, zooming in or out of metrics data is done in increments of 20% of the time interval that is shown. For example, if the chart displays metric values over a 5 minute interval, choosing Zoom In decreases that time interval to 4 minutes. You can change the zoom increment percentage in the Dashboard Preferences dialog box, as explained in Set dashboard preferences.
Zoom in and out as follows:
Note: When you click Zoom In, you zoom in to a percentage-displayed time interval. The default is 20%.
For general concepts regarding charts, see The Parts of a Chart.