I think the reason A&H gives you those seemingly inadequate specs is they are trying to deliver a product that has as low a price point possible to compete with a certain market. The USB port was expected to be used for board mixes which will end up as MP3 so the specs are simply "good enough for us" kind of idea.
They don't really even pretend to call it an Audio Interface. quote from the web page-
"ZED60-10FX comes with configurable USB audio in/out, making it easy to capture a stereo recording at the gig or in the studio." I was shopping for a new small footprint mixer last winter and took a close look at the Zed 10 fxs. I also looked at Mackie,Yamaha and Soundcraft offerings.
I determined that the USB port was of little use to me. I posted a question on another forum because the drivers are not even listed on the A&H web site. I was correct, they are generic and Sonar will hate them. So don't buy a A&H thinking it's an audio interface, It's a great little mixer. The USB will work to playback from your laptop , but it will not be any much different than using the headphone jack so no point in it.
I wrote a review-
http://www.gearslutz.com/board/reviews/843873-yamaha-mg82cx.html