Garmin run mode vs general mode

kelsully

I have a Garmin FR60. I wear a footpod anda chest strap. I get a pretty accurate mileage from the system and a calorie burn. There is also a general sport HRM function. I use it when I am doing a DVD or doing a circuit workout at the gym or whatever. I get a pretty average burn of 90-93 ish calories per mile...however when I use my HRM in the general mode...like when I am on the treadmill and my mileage is already measured...i feel like I get a higher burn...ie today I ran..5.14 miles with a pretty typical burn of 473 calories...when I did a 5.3 mile run on the treadmill last Wednes I got a 570 cal burn...that is a significant difference with there being not that significant difference in distance. Has anyone else discovered this discrepency with their Garmin or any other HRM and did you alter how you logged things?