The minimum reading is correct and the upper limit is a guess.
Immediately after Glug De' Dug, you come to Harrington Ledge. This one drops about 15 feet as well and is even shorter. It is not quite as intense because it is a little wider and doesn't have many features to it. Pretty much you start bookin' down a 45 degree ledge and try to keep your balance for the hole at the bottom.