In Scale mode you control how much to zoom into or out from a plot by using the wheel button on your mouse.
To scale a plot:
Select your plot and then click either Zoom in (
) or Zoom out (
Place your pointer on the plot and then rotate the wheel button to scale your plot.
Note: For 3-D plots, you can also place your pointer on the plot and then drag your pointer to the top or bottom of the plot window to zoom in or out.