Sorry for the delay.
You transfer them a small amount, and then dust sweeper uses it slowly to upvote the less than 0.02 posts/comments. So you get the upvote payout still. It does it just before the 7 days are up. And it will tell you when you have none left. I dont think they take anything for commission. I sent them $2, which should last a while.
Ok, I got that I think...