Was the last North Korean nuclear weapon detonation yield at Mantapsan underestimated by over 100%?

According to a Wikipedia entry here, the following formula is used to calculate the radius of the crater created by an underground nuclear blast:

r = 55 * ${\displaystyle \sqrt[3]{y}}$

If y was 100 kilotons as widely reported, for example here, the radius r of the crater should have been in the neighborhood of 255ft. with the entire underground void thus having a diameter of something like 510ft.

Yet the researchers referenced in this article state that the diameter of the void left under Mantapsan was 656ft.

That presupposes an r-value of 328 and thus a y-value of 212 kilotons, not 100, meaning the North Koreans detonated a weapon with a yield 112% higher than widely reported.