Auto Scale will set the chart so that the data is always viewable and will not scroll off the chart to the top or bottom when the chart data is moved to the left or right. Auto Scale is selected by default on any new chart that is opened. By clicking on "Chart Reset" and/or "Chart Home," the Auto Scale will turn back on. To turn off the Auto Scale, click the button or right click on the Chart Scale and drag up or down.
The Auto Scale can be selected from the toolbar shown below, by right clicking on the chart and selecting "Auto Scale," or by choosing the "Chart" tab from the menu bar and selecting "Auto Scale."