I'm obviously not BDZ and make no pretenstions to having anything close to his depth of scientific knowledge.  But I do have an idea about your question that might provide 1/2 an answer...

Your math says 200 MACE divided by 34 months of doing = 5.88 events per month.

But not all of those 34 months are equal....at the start there weren't 2,400 patients, that didn't happen til around February.  So I'm assuming the number of MACE was lower at the start when there were fewer patients and higher from February forward once the trial became fully enrolled...and I'm hopeful that a statistically and signficantly higher number of MACE are in the placebo arm.