Actually I also sent the same concern to the moderator of that group but he said that it's like Columbia Mafn (joining) 2012 ...Definitely on the lines of last year's group ...Columbia University M.A in Mathematical Finance class of 2013 would have been a better option
As a part-time student, my vote is to use the year of entry since I won't actually be part of the graduating Class of 2013, but it's not really a big deal either way . . . Anyone else planning to join have a preference?