If your eggs have a green ring around the yolk, it means

them (3-5cm of water above the eggs).
Heat to medium heat
Slowly bring water to a boil. Turn off immediately when it starts to boil vigorously.
Let it sit in water
Cover with lid and let the eggs sit:

9 minutes → creamier yolk
12 minutes → firm yolk
Shock cool with ice water
Transfer the eggs to a bowl of ice water – rapid cooling stops the reaction and prevents continue reading …