heart rate monitor question.

jeep4james

My heart rate monitor has a calorie burn function. I've always felt it would be the most accurate reading since it was measuring my heart rather than some average calorie burn from a machine or the app. However I noticed a while back while wearing it on a drive to the bike trail that even just driving for 40 minutes showed a calorie burn of over 200 calories. I know we burn calories all the time but I am wondering If that's the number I should be tracking now for meeting my calorie goals. For example if I do a 10 mile ride in 40 minutes should I count 500 calories or is the activity only producing 300 (minus the 200 for just living)? Does that make any sense?
It may not matter enough to worry about it but now I'm just curious...
Blessings, James