I removed my previous post until I thought about it a little more. But to answer your question the warrant holder always wants the highest price, So POET will have to do a good job keeping the share price well above the $2.16 threshold. If a warrant holder sold at say $2.25 and bought (exercised) at $1.80 that would only increase his or her position by 25% (if my numbers are right). Most of them will be greedy and hold out for little more. 

My previous post.

I also think they expect to be able to hit the $2.16 close price for the 10 days or they would not have bothered. Kind of a signal maybe that people should hold a little tighter to their shares at the current price. Hello to those trading for pennies.