Float isn't 1,511,380 shares: 2 things wrong here.
First, 471,766 was the float on 7/8/2016, not 2017. At that time the OS was 11,064,664. The rest of the OS was restricted shares, which vest out and free up over the course of 2 years max, but in this case much sooner. Restricted shares are not restricted forever. They become unrestricted continuously. So the float was about 10,000,000 before the Cowen dumping started.
Secondly, Cowen is not the only person dumping. He may be the biggest dumper at the moment, but there are others dumping slowly as well on the side, so just adding up Cowen's dumps will not give you the float.
Side note: since the float has virtually matched the OS, the OS has been increasing very fast in the last month or so. It is almost 20 million now.
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