What is Cao's puzzle?

In the movie "Reward", police officer Cao plays a puzzle of reasoning or logical reasoning.

He was answering how Lang Qing knew that coconut man was Li Jianhui.

Although the appearance, hair, body shape and personality can be changed, the scars left by the bride's fight during Li Jianhui's burglary are still there.

Make sure that the coconut guy around Lang Qing is the wanted man Lang Qing.