Setting Units in Data-Driven Charts
It's important to make sure your data-driven charts are clear and easily understandable. One way to do this is to set the units in data-driven charts when the numbers are large. For example, avoid using numbers in the billions. Input the full number in the chart worksheet, but set the chart unit to billions and the plotting engine (either Microsoft Graph for PowerPoint 2003 or Excel for PowerPoint 2007). The numbers will automatically adjust, both on the axis and the segment values. Just be sure to do this consistently and identify the units at the axis or under the chart heading.
If you have multiple data-driven charts on the slide, and the numbers are all in the same general range, set the units to a consistent level (thousands, millions, billions). Instead of identifying the units at every axis, you can then identify the units used for all of the charts in one prominent location on the chart.
Below are the menus for setting the units. See the "Display units" box near the center of both menus. The first is the menu in PowerPoint 2003.
This is the menu in PowerPoint 2007.