Skiing Burns 250 Calories/Hour

My friend has a tap and track app on his phone.  This is supposed to show you how many calories that you are burning doing certain activities.  He looked up alpine (downhill) skiing and it said 500 calories per hour.  My response was no way! Maybe 350 calories per hour.
I recently bought a new heart rate monitor that also tracks calories burned.  It's a Polar FT4. You enter your info such as age, sex and weight to help get a more accurate reading.
I wore the watch for three days of skiing.  I skied for 6 hours each day with one hour for lunch.  I skied one day at Sugarbush Vt and 2 days at Jay peak Vt mostly in the trees some bumps and limited groomers.
I don't think that tap and track figures in the chair lift ride with is about 10 minutes long.
I ended up burning 250 cal/hour and I was only in my target heart rate zone for 45 minutes out of the 6 hours.  Sorry, not an efficient way to get in shape and a few glasses of wine will kill that calorie burn!