[BUG] Description of the Mu calculation formula for the linKK function

[YaroslavBerko]

Negative values should be in the numerator, not the denominator.

\mu = 1 - \frac{\sum_{R_k < 0} |R_k|}{\sum_{R_k \ge 0} |R_k|}

Originally posted by @YaroslavBerko in c622f51