Today I 'lost' 81 rep due to serial upvoting reversal. How is this value possible?
- +10 for upvote on an answer.
- +5 for upvote on a question.
What am I missing that could contribute a +1 or +6?
You hit rep cap and the last vote you got only gave you ONE reputation point. That's it
One possible explanation would be that you've hit the rep cap, and some of the upvotes didn't gain you any rep, although they were still counted as votes.
Seeing how you were very close to the rep cap yesterday, that's probably it.