The Monkey King in The Journey to the West was put on a tight headband by Guanyin Bodhisattva to protect Tang Priest from going to the Western Heaven for Buddhist scriptures.

Although the Monkey King was brave, witty, clear about love and hate, and loyal to Tang Priest, Tang Priest didn't distinguish right from wrong, and often recited spells to make the Monkey King yield.

On his way to the Western Heaven to learn Buddhist scriptures, Bai turned into an adult for three times to play tricks on Tang Priest, and was caught by the Monkey King's "critical eye" and knocked him down with a golden hoop. The Monkey King wanted to get rid of all evils, but Tang Priest insisted that he had accidentally injured a good man. ...

The Monkey King wouldn't listen, and the Tang Priest recited the spell over and over again, causing the Monkey King to roll in pain.

Suppose the Monkey King's head is 20 cm in diameter. Every time Tang Priest recites a mantra, tightening it will shorten the original depth?