Welcome to FlyerTalk, Joey.

The seven seats - it could be they use some of the same GDS information we get via some of the availability tools listed in the Unofficial Users' Guide sticky (or not, it's speculation on my part,) which only show a maximum of 7 seats per fare inventory class, regardless of whether there are, say, 50 seats available (it looks like "J7 D7 I7" - which does not mean 21 seats, it means seven (or more) are available at those rates, but there may well be some numeric overlap.)

As to differences, the only way I can think of knowing that is to check the detailed fare rules - one can do that on aa.com upon selecting, but immediately prior to booking. I don't know how that works on Obritz, but add a layer on the onion when you add any special rules or conditions established by Orbitz itself.

We can feel your angst - stick around and you will learn much, plus there are links to some very useful tools and resources. (Be sure to check the Announcement for new members, the Unofficial Users' Guide sticky thread for links to the member-maintained Wiki on AA and other travel providers, as well as a number of interesting threads and useful tools.)