How to Get Subscript in Excel Graphs. When you create a graph in Microsoft Excel 2010, the axis labels and legend titles are drawn from the information in the cells surrounding the data. However ...

To change all data labels, click anywhere in the chart. To modify all labels on either the x or y-axis, click anywhere within the data series. To modify a single data label, click on the data label.

If you have uneven distribution of data in your Excel chart, here is a better way to change the automatic axis settings.