I was visiting my profile. I noticed a -43 change on my reputation tab header. Confused as to why I would lose that much reputation as I haven't done much the past few days, I clicked it. To my surprise, someone decided to serially downvote me for reasons unbenounced to me. Thankfully, the system reverted these votes and put my rep back to "normal".
However, my reputation tab appears to have miscalculated the delta since I last checked. All that was new since I last checked was a downvote on a question (-1), a serial downvote spree (-42), and a serial downvote reversal (+42). For some reason, the tab shows -43 instead of the actual delta of -1. I'm guessing this is a bug, but if it is status-bydesign, please explain why.