if a bunny eats grass that has 100 units of energy and the bunny get 10% how much is passed on to the next animal .​

This is an excellent source!

Example- The producer receives its energy from the sun, which is the ultimate source of energy. Meaning all the energy we use comes from the sun. Like I said earlier, the energy from the corn moves into the mouse. Not all the energy that the corn has is able to be transferred into the mouse, only about 10% of the available energy is transferred to each trophic level. A trophic level is the position an animal occupies in a food chain. And again only about 10% of energy is transferred from the mouse to the owl.

10%

Explanation:

https://hynemanbio.weebly.com/food-web.html

carbon atoms, hydrogen, oxygen, and nitrogen.