An answer of mine was downvoted and instead of decreasing my rep by 2 points it increased by 2 points. The downvoter removed his downvote. I did a recalc and the 2 points were removed from my rep.
This looks like a bug.
This happened because the post in question was deleted then undeleted. When either of these happens we sync up rep within 5 minutes...you simply did not wait 5 minutes.
Everything is working as it should here, you simply didn't wait for the 5 minute time period, which is how often we process these sync batches.