Ask T. He posted the example. If was for illustration of what these companies do.
I have a mathematical question for you:
The stock since Denner acquired (4.56 basis) has plummeted -75% to a low of 1.15 last Friday. How can he lower his basis to 2.39 without shorting?
Hint: you can "borrow shares" from a brokerage to short sell thus not affecting your position. No way he could have cut his basis in half without shorting because the stock - with the exception of the short term spikes to falling resistance - spent the majority of the time (since his ownership began) descending to the bottom. In other words, the profit was on the short-selling side.
It's a change of 1% of company ownership that triggers reporting. Not 1% of your holdings. Amarin has a little over 400 million shares open. So that gives the 4 millions shares to add or sell before reporting is required if over 5% ownership.
News 
Market Data 
Discover 
