The x-axis is the horizontal category line. Changes to the x-axis adjust the categories within this axis. You can also change the scale for the purpose of viewing a clean layout.

ADJUST THE AXIS SCALE ON AN EXCEL CHART Excel usually does a good job second-guessing me when it chooses the scale for an axis on a chart. But sometimes, to better focus some data, I need to adjust ...

Excel defaults to a linear scale for graphs, but you can easily change it to logarithmic to suit wide data ranges or logarithmic phenomena. The Chart Wizard produces graphs with linear scales.