Try graphing y = -1 * log(x) and imposing a limit on the upper bound of x and you'll get close to what he has. Perhaps that's the angle he's coming from. He provided the fitted equation further down in the featured article, and the log term does have a negative coefficient, plus an intercept term.
The graph he plots looks like the data fits the Exponential Distribution: http://en.wikipedia.org/wiki/Exponential_distribution