Sorry, and to piss everyone off, here is my final theory:
Amarin gets quarterly reports of total events (this kind of goes against what the company told me, but I'll throw it out anyway)
On March 30, 2016, they were told that there were 1000 total adjudicated events. The next day they began the 60% onset. They average 90 events per reporting period (quarter), so:
December 30, 2015: 910 events
March 30, 2016: 1000 (triggered 60% onset)
June 30, 2016: 1090
September 30, 2016: 1180
December 30, 2016: 1270
March 30, 2017: 1360 (will trigger 80% onset)
June 30, 2017: 1450
September 30, 2017: 1540
December 30, 2017: 1630 (will trigger 100% onset)
This theory would make the most sense except for the fact that it is my understanding that they don't receive events that systemically and infrequent... I know that safety checks are done approximately on quarterly basis, but not sure about event reporting. My understanding is that they come from 450 sites at different times... I'm not sure if they actually receive final summaries quarterly.