9) Here you can see how the blue line becomes dashed right near the 4th line marking 40% of the images since the Lower quality setting was changed to 73%.
10) The progress dialog for optimization is a little misleading since optimization will be complete at the point where the dashed blue line starts which will be 40% for this image.
11) Remember you can always hit the Cancel button if you want to make an adjustment to the Lower quality setting. Just hit the Optimize button again to restart the processing.
12) After Optimization completes, click on the Stacking tab to move on to the next step.