By “gas range” do you mean HV range?
What was your EV range when you began the trip?
Going uphill for 10 miles will certainly consume for fuel/energy than going 10 miles on flat roads.
From the info you’ve provided, you traveled 20 miles, 10 of which was uphill and potentially driven in a spirited manner. Your HV? range dropped from 65 to 8 on that 20 mile stretch. The range estimate is based on previous driving conditions. Perhaps you’d been averaging 40mpg, so the computer estimated that you could travel 65 miles with the remaining ~1.5 gallons in the tank.
Then the Pikes Peak Challenge began and you burned a gallon of fuel in 20 miles. Now, with a half a gallon left, the computer estimates you have 8 miles of range remaining, based on the previous driving behavior.
I’d recommend putting some fuel in the tank and charging the batteries prior to a trip. Unless you have Honda Roadside Assistance on speed dial. Assuming there is cell service where you get stranded of course.