I can't find it either.
I'm not sure how much weight to give these historical rankings, given that most of them are hypothetical calculations on what rankings might have been for players who retired long before the ranking system was introduced. Where's Jim Laker on the all-time offspinner list, for example?
I think we can all agree though that Ashwin has had a magnificent couple of years.
But for me, he's got to succeed outside Asia to be considered an all time great, whatever the rankings say. I'm not saying in every country - almost no-one has an unblemished record everywhere (Murali didn't do so well in Australia and Warne not so well in India, and they're both greats). But Ashwin hasn't really succeeded so far outside the subcontinent, largely because he hasn't had the opportunity (one fairly poor series in Australia has been pretty much it). That's not to say he won't succeed elsewhere, just that I won't regard him as in the same league as Warne, Murali, Underwood etc. until he does.