Question on weighted similarities

[yamo93]

Hi all,

I have a question on the formula used for weighted similarities in the 
class AbstractSimilarity.

I expected to find a simple percentage, as
      double scaleFactor = (double) count / (double) (num + 1);
      return result * scaleFactor;

But the the code is more complex.

What are the benefits of this approach ?

Rgds,
Yann.