I am doing mostly TRX and elastic band work as strength training and am seeing that the device is very bad at counting reps. I am curious as to does rep counting only work for the set of exercises built into the device or does it not work well at all? Also is there a description anywhere of how garmin defines what some of the exercises are so that I can pick ones that are closer to the TRX work so that perhaps I can get it to be more accurate.