Treadmill & Elliptical CALORIES BURNED

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Does anyone know how accurate the "calories burned" number on a treadmill and elliptical are? I find it hard to believe that I do cardio run/jog/powerwalk & at a 3.5 - 7.0 incline for 35 to 45 minutes and I only burn 190 calories?! Any input on this will be awesome! Thanks!