Another Question: accuracy of cardio equipment calorie counts

How accurate are the calorie counts on cardio equipment?  I have heard they are fairly accurate once you enter weight, age etc.  

I saw someone write the other day that the machine includes the calories you would burn any just from being alive.  So if my baseline that I burn in a day is 1400 calories and the elliptical says I burned 300 calories in half an hour, that wouldn't bring my total for the day to 1700, but more like 1670.  Is that true for all machines? most? any?

I think you're starting from the wrong point.

As a benchmark, reasonably active adult women need about 1900-2100 cals a day to maintain their weight and stay healthy.  1400 might be the amount you used lying flat on your back doing nothing whatsoever beyond breathing...  If you just move around normally doing everyday things that could increase to 1700-1900 quite easily.  If the machine says you've used 300 in half an hour's physical exercise then it gets added on top.

Try using the CC calculator.... if you typically get half an hour of exercise a day set your activity level to 'light' and work with it as an average. 

Right, I know about the calculators, I just wanted to know how the monitors on cardio equipment work.

Cardio equipment monitors aren't all that sophisticated   They  calculate on a combination of time, speed (revs or similar) and (if requested) the weight/age/gender of the individual and then spit out a best guess number at the end.  The only way to get a really accurate 'calories burned' number is to be connected to breathing tubes and monitors.

The 30 cals difference in your original example is about the amount of energy in one peanut and won't make an iota of difference to your weight.  Which is why I suggest that you work with a reasonable average instead.