Ken over at Sports Club Stats has been making a bunch of changes, including the incorporation of the "New and Improved"* tie breaking procedures (including the disciplinary point tie-breaker), and probably a cleaner breakout of where everyone ranks against each other, since there is no more playoff qualification cross-over between the East and West conferences. Anyway, I am the main updater of the data on a day-to-day basis, so if y'all want to take a look, please do so. Some of the new features include Probable Playoff Opponent, Chances for Wooden Spoon and Supporters Shield, standings per League, and per Conference. Most importantly, please let me know if you find problems or errors in the data. I have no control over what is calculated, but I can generally correct errors within those calculations. *Put in quotes because however new, the improved part of the statement is debatable.
More or less what VanderDeckenIX said. It is the "matches in hand" that team has on the team that has played the most matches. In this case, Montreal. Montreal has no matches in hand, because they've played the most and Columbus has 6 matches in hand because they've played the least (6 fewer than Montreal).
After the mid-week games on Aug-29, the playoff odds (http://www.sportsclubstats.com/USA/MLS.html) for Montreal & Chivas are at 5.4% & 2.8% respectively, while Phily & N.E. are practically 0.0%... The fight is now down to D.C. and Crew...
Through 3-Sep, the playoff odds are: S.J. - in ... Vancouver still at 89% Crew up to 76.1 % D.C. down to 57.3% ... TFC - out