Blackrock upped their stake from 1.823 million shares to 2.35 million.
Or from 5.67% to 7.25% ownership.
Not sure where you got the 1.823 million shares. Nasdaq shows that Blackrock had 913,610 shares at 9/30/12. That's a jump of 1.4 million shares in the last 3 months of 2012!!!