a bit confused on something..

they are saying that based on the assumption that you are only eating up to 1200 calories a day. If you burn 200 through exercise you are then basically getting the nutritional value of 1000 of the those calories not the full 1200 that your body needs to function. Hence why they say eat your exercise calories to ensure your body gets the nutrition it needs.

when you started on this site you had to set an amount of weight you wanted to lose each week your daily calories are then set to achieve this weight loss with out doing any exercise what so ever so when you do exercise you can eat the calories you have burnt and still achieve the weekly weightloss you set for yourself. I personally try not to eat my exercise calories in a hope that it with help me lose the weight that bit quicker that being said if I do eat into them I'm not too hard on myself cos I earnt them x

Basically, it's to make sure your body gets enough nutrition. You're already eating a deficit of anywhere from 250-1000 calories. Burning calories through exercise puts you at an even higher calorie deficit. You need to eat the same amount of calories that you burn in order to get enough nutrition and make sure your metabolism doesn't slow down.

When you log exercise, MFP adds cals to your daily goal to account for the cals you burned with the exercise. Since MFP automatically calculates a cal deficit for you (based on your chosen loss/week goal), if you don't add extra cals to your daily amount, you would be at a higher daily deficit than you wanted. MFP uses the 2 lb/week loss as a max, as more than that is unhealthy/unsustainable for most people.

Make sense?

Yeah I see no purpose it eating them. I eat around 2000 calories a day. I burn about an extra 500. And my workout burns another 600-900. So eating those would be stupid! Unless I am happy with like 1 lb a week.

For most people, a loss of more than 2 lbs per week (after the initial higher losses in the first couple weeks of water weight) is unhealhty, unsustainable, and likely leaves them in the position of depriving themselves to the point that they binge and/or give up. Losing weight too fast stresses they body's systems and can lead to organ damage. Most people who lose faster than that end up regaining it, and more. That is why MFP limits the max loss to 2 lbs per week.

Read the threads I suggested in my previous post and you'll likely have a better understanding of why so many people recommend it - it is backed by a LOT of research.