reserve 4m cts - is it real?

In the 30/10/09 Activity report stated combined reserve of over 4M carats in ground for 3 pipes out of 11 (9 already been mined by RIO before selling to NAD). However, previous 9 pipes only generated 500,000 plus carats. I doubted much on existing 3 pipes figures! Either previous 9 pipes figure were wrong? Or existing 3 pipes' figure are too high? Did Rio know that the remaining "3" had so huge reserve that they didn't mine them and leave them to other buyer! Or they made the wrong decision to mine the 9 pipes with less diamonds! What gone wrong with RIO? Will there any more reserve left under the 9 pipes? Or were those 9 pipes digging not deep enough to extract their real value? Can those 9 pipes re-open again to explore their real value? If any of you get the chance to attend next week AGM, kindly raise this question for me to Mr. Reddicliff. He should be the only one that can give a satisfactory answer. Tks!