Let us look at how we calculated the previous confidence level graphically.

First we determine the confidence interval that has an upper limit of 1.00 (based on the point estimate for survival of 0.72, and the standard error of 0.192). In this case it is the 93% confidence interval (ie the 93% CI is 0.52-1.00).

Thus, 7% confidence lies outside this interval, half on either side.

So if we add 93% to 3.5%, we have 96.5% confidence that the hazard ratio is below 1. That is, there is a 96.5% confidence that a survival benefit exists (and thus only a 3.5% confidence for survival detriment)