Reword for clarity

README.md

@@ -76,7 +76,7 @@ gem_specs.versions_for('pundit')
 
 ## Health Score Formula
 
-The formula takes the contents of `Gemfile` and `Gemfile.lock` and produces a decimal number in the $[0,100]$ range, representing the health score based on which dependencies (gems and Ruby) are outdated and vulnerable to known security issues. 100 means everything is up-to-date and there are no security issues, and it lowers as newer versions are released or security issues are discovered.
+Health score is calculated with a formula that takes the contents of `Gemfile` and `Gemfile.lock` and produces a decimal number in the $[0,100]$ range. 100 means everything is up-to-date and there are no security issues, and it lowers as newer versions are released or security issues are discovered.
 
 By design, health score is most useful as a relative measure of application health: if your health score suddenly drops one day from 100 to 90, it signals a serious issue (e.g. a new vulnerability in your Ruby version). If it drops from 100 to 95, it may signal that a new minor version of Rails has been released, for example. If it drops from 100 to 99.5, it may mean a gem like Pundit has a new patch version with a bug fix.