The fitness test allows it to have some basis for judging your relative fitness, otherwise HR numbers by themselves are meaningless. My LT could be your max HR or vice-versa. IIRC the fitness test on my polar basically established a VO2max estimate as well as an HR range so it had a better idea of where your HR was relative to your limits. If you haven't at least done that I wouldn't even think the calorie numbers would be in the ballpark.