Sorry, your question is quite confusing to me?. Are you asking "How FaceBook and Twitter help in Google Ranking.......?"
not sure exactly how google count it.. what just Matt Cutts said about it is they consider it but it depends on the quality of it..
Read SEOMOZ blog, There is one post that I have read regarding this. The guy explain nicely the twitter parameters which will be counted for ranking on google.
Social media can improve the Google rank as there are two ways of improving SEPR. One is SEO and other is SMO. Facebook and twitter sites come in social networking category so it can help improve the SEPR.
Yes, social media helps to improve ranking position. Read good article about it seomoz.org/blog/tweets-effect-rankings-unexpected-case-study