This is ridiculous. I didn't hear the show yet (I'm listening to the replay now), but I heard the H100 News segment about it.
Here's what I think the issue is now... It seems that if the number that represents the circumference of the chest goes down, the cup size goes up. But the confusing part is the volume of the cup itself is proportionate to the measurement around the chest. The volume of the cup can be vastly different with regard to bras with the same cup size. In other words, a 30 D will have much smaller cup volume than a 34 D.
I could be wrong. That's what it seems like to me.
Another way that I'm thinking about it is I have a mental image of what D cup boobs are, and the body type that they would be most proportionate on. This would be a woman with a larger measurement around the chest area. If we were talking about a woman with a very low measurement around the body (let's say 30"), what I visualize as "D cups" will actually be a much larger cup size on her. Maybe an F or G.