from my understanding, i asked once what the accuracy is from those machines, and i was informed that they aren't very accurate. unless you can change the settings for weight and age and all that jazz.

using my polar hr with the stair stepper maching at my "gym" i got a slight discrepency (about 20 cals) but i could also change the age and weight.

is your watch set up for you? i'm assuming it is, i would personally go with that number rather then the one on the machine.