It was in an article I read, I think it was by minnowbooster, but I might be remembering that wrong. They said it will change after the hard fork 2. Lots of times I read that to maximise your vote you should vote after 30 minutes of post release, but the 15 minute mark means more weight to the author, I think, anyway I am not that clear about the different types of steem value. Congrats on the $100 post!