Have you checked how many Seeders/Leechers you allow as maximum in preferences?
Edit: Also, if you got 10 active clients out of (104), you have to check how many seeders that is active aswell.
If let's say there are 400+ active seeders, all of theses seeders are havin a "war" for all these 104 active peers. In other words your tracker is looking for free spots out of all these leechers and are fighting against the other seeders for speed. So your seeding is searching for free spots which isn't already taken and calculates the other seeders upload speed/availability etc and calculates how much out of these that can connect to you, and in that way decides your upcoming upload speed. The more seeders -> less spots to grab leechers. So the best upload torrents would be the once with small amount of seeders and a high amount of leechers. That way you will have a greater chance to maximize your upload speed.
