The 64% is still 64% because if N is big enough it almost doesn't depend if you consider something with a probability of 1/17 in 17 days or something with a probability of 1/21 in 21 days.
The 64% is still 64% because if N is big enough it almost doesn't depend if you consider something with a probability of 1/17 in 17 days or something with a probability of 1/21 in 21 days.