What axis displays incremental values to identify the values of the data series?

ValueAxis is the class which opens up value axis on the chart. The chart can have any number of value axes. For a Serial diagram, one value axis is created automatically. For XY Chart two value axes (horizontal and vertical) are generated automatically.
Value Axis
The chart element that displays incremental numbers to identify approximate values, such as dollars or units, of data points in the chart.

How do you change the scale of a chart axis?

In a chart, click the value axis that you want to change, or do the following to select the axis from a list of chart elements

On the Format tab, in the Current Selection group, click Format Selection.

In the Format Axis dialog box, click Axis Options, and then do one or more of the following: