It seems that the opposite is true (they underestimated the time spent in the cave): 40 days seemed like 30 days for most and even 23 days for one volunteer, ac

It seems that the opposite is true (they underestimated the time spent in the cave): 40 days seemed like 30 days for most and even 23 days for one volunteer, according to The Guardian article (https://www.theguardian.com/world/2021/apr/25/deep-time-team-ends-40-days-underground-in-french-cave https://www.theguardian.com/world/2021/apr/25/deep-time-team...).