The Space Wolves did take quite a few losses fighting against the Thousand Sons and the Alpha Legion during the Heresy, that being even before the Traitor Legions reached Terra. The total amount of casualties that they are believed to have suffered are, at this point, unknowable and even a ballpark estimate would be monstrously inaccurate. Once the series is concluded...in...a long, long time...we can then debate the full scope of the Space Wolf Chapter as it is today. I would agree however that the Space Wolves are greater in number than a standard chapter.