When you've shifted the scale range or zoomed in or out on the y-axis for a group of analogs, you can reset their pens on the graph.
1. Click the currently selected pen in the pen legend (i.e. a selected pen is one with a rectangle displayed around it in the pen legend). The formerly selected pen should now be deselected (i.e. no pens should be selected in the legend).
2. Click the Reset Y-axis (Analogs Only) button.
The plotted data for all analogs will be reset on the graph.