That thing is probably not very accurate.
How do you measure calories burned after all?
I'm not sure it can be done accurately enough to be useful. And I don't think this machine is worth the bother.
As Gary Taubes argues, eating by balancing calories is impossible. You would have to balance input/output by less than 1 percentage per day to avoid getting fat. If you overeat by one percentage a day for ten or twenty years, you will get fat.
Obviously, this is not how the system works. Our body does not count calories. Alas, counting calories does not help you.
Regulation of body mass is a lot more complex than the input/output theory suggests. Luckily, the solution is simple:
Eat real (paleo) foods and trust your hunger.
What you are experiencing is probably just a good example of how inaccurate calorie counting is as a guide for eating.
So, yes, that online calculator is BS. And so is that device. Don't buy :-)