When you first start steemit you're given a reputation of 25 it's actually it's very weak and a downvote if 0.10$ can bring the reputation down to 20 an opposite UPVOTE of the same 0.10$ can increase the reputation to 27.
The truth is reputation score is uplifted when you receive upvotes and the higher you go in reputation, the harder it becomes difficult, for example it become difficult when you hit reputation of 50 it even becomes harder when you hit 60 and extremely difficult at 70.
My point is upvotes bring about rise in reputations and downvote simaulteanously brings out reduction in reputation.