Why does the nutritional value of a hard boiled egg differ from the nutritional value of a fried egg?

From Livestrong, a hard boiled egg has 70 calories and a fried egg has 90. I realize they are considering the egg fried in grease or oil, but If I'm frying my egg in a non stick pan with a spray of pam, why should they differ?

Is this a scientific fact? Does the chemical makeup of the egg change providing different nutrients based on the method of cooking?

If I am frying without fat, I would go ahead and use the nutritional value of a raw egg. Or, I would split the difference, as I am skeptical of the claim that cooking spray adds no calories at all to one's food, and call it 80 calories.

In general, it's best not to expend too much energy worrying about things at the 10- or 20-calorie level, because most of the time your estimates are not going to be that accurate. I recommend that you presume you overestimate some things, underestimate other things, and it all comes out in the wash.

Ditto what Carter says, but it does bug me that on so many apps they automatically add calories for frying because how can they know how much fat im using? But of course, it's not like all eggs have the same calories either. What I tend to do is to just put raw egg and then add whatever fat I'm using for clarity. With something like eggs, you do eat most of the added fat. Not so simple when it's something like fried chicken or breaded and fried anything.

The different apps and calorie suggestions on the internet also bug me. I just gave up and just do the best I can.

However, I do count an additional 5 calories for the Pam cooking spray.