Well I ahve figured that size 4 and 6 is purely for pre pubescant girls who nowadays shop in grown up shops when they shouldn't.
When I was a teen, there was no way I could go into a high street womans shop and buy clothes that would fit me. I had to shop at Tammy Girl (remember them?!)
Now we are made to feel bad, caue there are lods of smaller size in OUR shops.
Ban these pesky teens I say.