The Auto-Scale feature controls the price scale on the chart. When ON, the charting application automatically changes the price scale to match the high and low prices currently in view on the chart window. As you scroll the horizontal time scale, the price scale is automatically adjusted.
You can tell that Auto-Scale is ON when you right-click in the price scale - the Auto-Scale option is grayed out.
Auto-Scale OFF
When Auto-Scale is OFF, the charting application does not change the price scale to match the data in view on the chart window. You are able to scroll the chart image vertically by dragging the body of the chart up and down.
To turn Auto-Scale on
If you have compressed or expanded the price scale and wish to turn Auto-Scale on, right-click on the price scale to display the context menu.
Select Auto-Scale Y-Axis.
Note: Auto-Scale, by default, is turned ON when the charting application is opened.