Turns refer to the total number of people in line ahead of you. However, these number can be deceptive in some cases. If you go to the game detail page, there will be a tab on the side listing the "Trading Info." You'll probably see that lots of people have the game on hold (which means they're current inactive in the queue) or they don't have enough points, trade credits, or trade slots available. The middle column will tell you how many people are "ready to trade" - this is the realistic number of people ahead of you.
There are a lot of cases, especially with high-value games, where you can get matched even if you have a long wait! You can also check out the number of trades going on right now, and the number of times the game has been traded in the past. Generally, the more it's being traded the quicker you can expect the queue to move.
It's very important to list the games in your library correctly - if you offer the game as disc only, you won't be matched with someone requesting full package. However, if you don't send all the things you promised, at best you will receive a "neutral" feedback and probably a scathing comment from a justifiably pissed-off buyer. More and more people have been complaining about this system though, so it's very possible that they will leave a negative out of spite, leaving you with no points and no game. You REALLY should not try to cheat the system by listing games incorrectly, and the fact that you're asking about it right off the bat seems to be a bad sign. Don't try to rip people off, you'll be around a lot longer that way.
