Litebulbs - It says "more than 900" crew have accepted the offer, not "only 900".
What Willie Walsh (according to other reports) said was that if Unite's claim that there were only 900 cabin crew that aren't in Unite was true, then all would have accepted the offer on an individual basis. This is where the claim of "more than 900" seems to have come from. That's not the actual number that have accepted. I suspect Willie will be keeping his cards close to his chest for now.