If the value ranges of data series vary considerably or if mixed data types are used, you can plot one or more data series to a secondary axis (Y axis). For example, you can plot the number of houses sold on the left Y axis (primary axis) and the average price on the right Y axis (secondary axis).
You have a chart with two value axes and you want to plot a data series to the second value axis, the secondary axis (see also Formatting Axes and Grid Lines ).
If a value axis is not visible, select the property Visibility.