Or it could just as easily mean that 18% succeed the first time, and the second time (after either an exit or a failure) only 2% more succeed Which you could t

Or it could just as easily mean that 18% succeed the first time, and the second time (after either an exit or a failure) only 2% more succeed Which you could take to mean "If I don't succeed in my first venture, I am not part of the 18%- so am I part of the +2%?"