If you include their matches from 2007 and 2008, as you do, then you must go with the Masters schedule of the time. Or you have to say it's "9 out of 10" (or 11, if you count Madrid Outdoors and Madrid Indoors as separate events).
No need to argue, but there always have been 9 "Super-9/AMS/Masters 1000" events per year.
Judging by the no. (yearly chronology) of each event they played (indian wells - no.1, madrid 2009 - no.5 etc.), they played in 8 out of 9 events during those 3 years...
If they had played madrid '07 or '08 or shanghai '09, we could have said it is 9 out of 9.