NIS 2011 - Application Ratings

I am totally confused about the results of applications rattings. Immediately after installation I had results of 98% trusted applications.
Now after a few days the percentage of trusted applications decreases and now shows 58% trusted applications. Why does this happen? After installation of  NIS 2011 I do not  install new programs.

Scan profiles performances is set to Standard Trust. The question is whether the percentage of trusted applications will be increased or something I should do?

 

I ask this because it is explained "more trusted applications less scanning" and consequently this improves the experience during work with computer.

I apologize for grammar errors. Google translate is my friend :)