FR60 Calories Burned Calculations

I had my first opportunity to test out the updated FR60 firmware that supports calculating calories burned when using the watch in "other" mode (i.e. no foot pod or cadence sensor).  According to the watch calculation, I burned 662 calories over an intense 45 minute spinning class (Les Mills RPM).  I don’t remember the exact calories burned totals for the same class from my Sportline HRM, but I think it was about double what the Garmin is reporting.  After spending a few minutes Googling for some web based calculators to determine calories burned, I actually think the watch is pretty close.  Another calculator that took into account most of my physical traits came up with 670 using length of workout, average heart rate, weight, age and an assumed VO2 max of 35.  Les Mills also reports that the maximum burn during one of their classes is 800 calories with an average of 600.  While this is good news about the updated firmware, I think the local Les Mills RPM instructors need to quit telling us that their classes burn up to 1,600 calories per class.  Even the Les Mills site doesn’t make that claim.