Statistic rebuiding doesn't do it

Hi,

I've installed Organic Group Statistics and I've run the "Rebuild OG_statistics". It said: "Remaining 0 of 2" and then: "Statistics rebuilded successfull".
But when I try to use "Members count" in views, only the most recent two groups return the right number of members, all the others return 0.
Of course I tried running the rebuilder more than once and I flushed all cache, just in case... But nothing has changed.
I attach here a screenshot of the view, maybe it can be useful...
Thank you