When you add a new chart in PowerPoint 2013, you will see that it has its roots in Excel — all the chart data is also stored within an Excel sheet. When you edit chart data within Excel, the process may not be limited just to changing the values. You many also need to add a new Series or Category. If we use a column chart as an example, Series within your Excel sheet show up as the columns. Categories on the other hand are essentially a set of series.