Donna, this "chance of survival" business is a statistical construct. All it means is that in a group of some number of members who share a common condition, at the end of 5 years (or some other period), some percentage of that number will still be surviving (unlike the rest of that group.)

Unfortunately, it tells you exactly nothing about your chances as an individual in that group.

In every group of some size, individuals who meet all the group's requirements will fall outside the predicted outcomes (on both the high and low ends) but there's no data to help predict who those individuals will be.

It's frustrating for folks in our situation, but like everything else in life, it is what it is.