This chart demonstrates the reduction is usable energy from high amperage discharge. At the highest reported discharge current (570A) the cells deliver just 19Ah over the course of 2 minutes. I am more concerned with the 1hr and 30min specs, as these correlate with the amount of current usable for my commute with and without the ability to charge at my destination.
By plugging all the values appropriate for the 240z into this handy calculator I get a pretty good estimate for the current draw at different speeds for various incline and wind situations. It happens that the 30min draw of 96A works out to be about 70mph on flat ground, while a draw of 53A is 55mph. I also see that I can travel 30mph for 5 hours, or 90mph for just 12 minutes.