I have no idea where they get those figures from to be honest. Though it doesn't surprise me that they (just possibly) maybe don't know how their own back end systems work because, as we all know, they are so "pigeonholed" that the person who documented those figures to inform end users probably thinks they are correct, when infact they aren't. I'm 99% certain I'm right though, based on past experience when I had broadband MAX on a 60dB attenuated line.
For further clarification of how it all works, see this
other recent post I made a few days ago.