Interpreting Cardio Equipment Readings

JBliss1108

I used the elliptical machine at my gym this afternoon, and for 30 minutes worth of exercise the machine gave me the following information:

Avg Watts: 183
Ave Mets: 9.8
Calorie Burn: 360

I'm a 34 year old male, 6'0", 245 lbs. I don't know what watts and mets are, so I was curious if 1) could someone explain watts/mets an if they are related at all, and 2) given my personal stats and the watt and met numbers, is it possible to determine if the calorie burn the machine provided is close to accurate? I normally discount the machine readings by 30% or so and log that number, so today's calorie burn was logged at 250.