I use the bodybugg calorie counter (an arm band you where with five sensors on it that tracks your calorie expenditure within 92% accuracy) to track my calories every day. It's a really neat program (but expensive at $500 for the arm band and a monthly fee for the website subscription) and I'm pretty confident that it is fairly accurate. I used to think that what I was seeing on the readouts for my workout equipment was accurate and came to found out that in most cases that was far from the truth. However, in your case, I would say that the 149 calorie readout is much more accurate than the 59 calorie one (Lord, would any of us EVER workout if that's all we burned??!!??!). I weight about 240 pounds and recently brought in the groceries from the car and put them away. That was about 30 minutes and my program says I burned about 78 calories in that time. A steady walking pace would, obviously, get you more then that so between 150 and 180 sounds about right...probably, unfortunately, closer to the 150 range!
Good job on the workout...that's more then I've done today! Ugh..