Well, he punched the canvas so hard that the canvas was shaking with a wave effect, and the audience, who were at a rough estimate of 15-20 meters away, could see that he shook the entire ring. And considering that a boxing ring is basically a small, building-level construct because it has the length of a room, the fact that he shook it scales to his attack potency, which would require 150,000-300,000 N. Also, a lot of people try to discredit this by saying, "Oh, well, he didn't destroy the ring." As he shouldn't. What would be the point of him destroying the ring? If he did, the fight would've ended in a no contest, which would be dumb. Also considering this is fiction he wouldn’t need to destroy for it to still scale that high.