When RubyCritic runs, each analysed class or module gets assigned a rating - a letter from A to F, A being the best. This serves as a baseline to tell you how smelly the code is. Generally A's & B's are good enough, C's serve as a warning and D's & F's are the ones you should be fixing.
Similarly, a global score that ranges from 0 to 100 is calculated, where higher values are better - less code smells detected. This provides a quick insight about the overall code quality.
RubyCritic's rating system was inspired by Code Climate's, you can [read more about how that works here][1].