It is said that it is an egg that can hatch chickens and is very nutritious. Some people look for this kind of egg to eat.
Two of them appeared in the eggs I bought the other day.
I'm not sure whether your situation is the same as what I know, but the surface features are the same.
I ate a red one when I was in kindergarten, and it didn't scare me to death. I remember it for more than ten years.