Problem:

Lately, I've started exercising in the gym and outside. I've also started to look at the details of food I eat.
Food usually has a label saying the amount of energy is inside it. For example, some chocolate says it has 400 kilocalorie for 100 grams.
I have some questions about that:

Question: Does the label say the amount of total chemical energy exists inside the food, which will be released if burned, or the energy available to the human body after digested, and because digesting requires energy, the food contains actually MORE energy then written?

When I'm riding on a static bike, it has a screen which counts the kcal I burn. It has a thing connected to my arm, measuring my heart beat. After about an hour of riding, it said I used about 700 kcal. Is it the amount of work I did, i.e if there was a battery connected to the bicycle, I'd generate 700 kcal of electricity, OR, the amount of energy my body LOST, because muscle efficiency is far from 100% (so, I lost 700 kcal, but generated only 150 kcal of electricity, for example)

Question: When doing a physical activity, the heart beat and breathing rate increases. Lets say I'm riding a bicycle or running.

Question: What is the ratio between energy consumed by the muscle to energy consumed by the lungs or heart?