I know this post was from a while ago, but just thought I'd share I trick that I use when on cardio machines that count calories.
I've read a few different places that those machines can be up to 10% off, so I generally take the calories it says I burned and multiply them by .9.
This number tends to line up much more with what FitDay claims I'd burn in that time, and, since getting a HRM, I've noticed that it and FitDay agree quite a bit on calories burned, which to me, says that FitDay's pretty wonderfully accurate (and therefore that the multiplying-by-.9 method isn't half bad, either).
Starting over for the last time.
Start Weight: 141 lbs
Current Weight: 139 lbs
1st Goal Weight: 133 lbs (7/21)
2nd Goal Weight: 125 lbs (8/31)
UGW: 115 lbs (11/20)