Under field conditions, this whole chart is going to be affected, to a considerable degree, by the difference in elevationbetween the peep and the nocking point. The chart appears to be the actual flight of the arrow. But when the sights are 4" above the arrow, the difference between the sight pins at the various distances is less than the chart would suggest. The arrow is flying uphill quite a bit when the sights are level.

For instance, for my 260 fps setup, the actual 30 yard drop is slighly less than 6" relative to the 20 yard pin. The difference between 60 yards and 70 yards is about 25".