This absolutely the right place to ask!
The Armor Class system is a system used only here and is not found on Wookieepedia. It is a relative system that gives a rough idea of the quality of a piece of armor.
Typically, stormtrooper armor is Quality 5 or so. Quality 1 would be your standard clothing. Quality 10, well, I haven't seen any Quality 10 armor, and I'd be very hesitant to approve of a submission of Quality 10. Quality 10 would be akin to Terminator plate from Warhammer 40k, or Gnome armor from Battletech. It's impervious to just about anything. You don't see it often, if at all, in Star Wars.
Please also note that the Quality rating is often viewed on an exponential scale in terms of requirements. It's quite easy to go from Quality 1 to 5, or even 6. That's all fairly common armor. The material and development requirements of Quality 8+ is exponentially high, however.
Finally, you can have different Quality levels for different types of elements. For example, armor may have separate Quality ratings for energy protection and physical protection.
I hope that helps. Please let me know if you have further questions!
[member="Gezes Skel"]