The minimum reading is correct and the upper limit is a guess.
After 1.25 miles of warm-ups and great surfing, it's time to face the first ledge chute. You know it's coming up when you pass the first shale cliff on the right side on a gradual horseshoe bend to the left. You will then round a right hand bend and immediately begin to descend through Glug De' Dug. Watch your elbows if the water is low as it channelizes into an actively erroded chute no wider than 6 feet. This short ledge drops about 15 feet. You may want to scout it on the right side to make sure it's free of wood as it is a blind entry.