The MLS simply gives data for listings put on the MLS itself. So if there are new homes on the MLS then that particular home that closes on the MLS will count as an MLS sale. However, if there are 20 other homes in the development that sold that month but they were not on the MLS then they will not be counted. As for the differences between the MLS and Jims number it all depends. Also make sure you check to see if the number is a total of ALL TYPES of homes or not, (attached, detached, multifamily) as Jim may parse things out in a more granular manner.