"If the event rate is 7.2% and management says that we have about 10 to 15 events per month or an average of 12.5 events per months, we get a sample size of 2084 approximately."

I don't follow that math. The 7.2% is an average event rate based on cumulative patient years. The 10 to 15 per month is likely a snapshot of the event rate during the past few months. Full enrollment was achieved in March. I provided Pomp some perspectives on patient years and events in my reply to the original post "Patient Enrollment Modeling." 

As for the rest of post dealing with RRR, lots of possibilities ranging from 0% RRR to 100% RRR. Your numbers may work out for that possiblity, but a ton of other scenarios are also possible.

BDAZ