I think there's an error in

This formula

sqr((ior−1)/(ior+1))/0.08

(if SQR stands for "square root of") produces not the same result as of it mentioned in documentation.

Ex:
In "For example" section there are a set of statements, like this:
... water: ior = 1.33, specular = 0.25 ...
But for with this formula it would be sqr((1.33-1)/(1.33+1))/0.08 and it equals 4.704235148 and not 0.25.