Calories burned

does either of them take into account your height and weight? the more you weight, the more calories you burn, besides that different systems come up with different results, my stationary bike says i burnt 200 cal and mfp says 264, i just do the exercise to become healthier ( better circulation)and to build muscle (because muscle burns more energy and it tightens your skin and body shape) .

The calorie count is just a motivation, let's face it, it's a bit difficult to calculate exactly how much you are burning as this depends on your fitness level, muscle and fat ratios, what are you eating....etc.

your clothes are the best judge, if the trousers are losening up you are losing weight if they are tighter you are putting it on, even scales can be deceiving as they don't discrimanate between muscle and fat (not all, anyway).

Enjoy the exercise as a challenge, today you do 20 min, tomorrow it gets easier and do more and soon you start feeling great, with more energy and a spring in your step.

take care.

well you didn't burn 300/400 calories walking for 20 minutes (well it's pretty unlikely) so I'd suggest map my walk is wrong. They are in fact all estimates considering the accuracy of most machines in a gym i'd think they're both wrong