Oh, I had some trouble wrapping my head around the idea. The older people count out slowly by as much as 40 seconds. They are inferring that the perceived time for the older folks is faster.
The article is wrong. From the book itself: "The older group, ranging in age between sixty and eighty, were off by forty seconds. Not far off, but if we were to extend the counting for, say, one hour, it would amount to more than thirteen minutes."
That's 30min + 13min.....they are counting slower....not finishing the task faster...