And just like with every thing else, we all lose in different areas. Some people will lose more around their middle, others will lose more in the rear end, and others will lose breast mass. Everyone is different.
A good point was made up though, if you take a 34B bra, and a 40B bra, the cups are bigger in the 40, because the A,B,C, etc. is only meant to mean the "projection" of the breast. A person with a 40 band size will have "wider" breasts than someone who is a 32 or 34...if that made sense.
So, if you start at a 40DD and end up at a 36DD, your breasts did actually get a little smaller, but they kept the same proportions as they were before to your ribcage.