哑巴吃饺子，心里有数

哑巴吃饺子，心里有数

Literally means:

A mute cannot talk, so when he eats Jiao Zi or Chinese dumplings, he is unable to describe to others how they taste, though he knows it very well.

Actually means:

It figuratively means that one knows exactly how things stand though for some reason he has to keep quiet about it. It usually refers to things that are inconvenient to talk about.

哑巴不能说话，所以吃了饺子，不能告诉别人饺子怎么样，但自己心里很清楚。比喻嘴上不说或不能说，但心里很明白。多指那些不太好说的事情。