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Don't worry about it @smailer. It's not your upvote that reduced the author's income. One reason is the inflation of the value of #STEEM. Others could be the downvote made by other members. Can't blame it on yourself.

Here's a parody that might want to lift your spirit up -->> https://steemit.com/steemit/@cjclaro/steemin-away-a-parody-of-dumb-ways-to-die. And you can upvote this one, too! ;-)

Have a great day!

That's happened to me a few times and I don't understand

I haven't had that happen to me yet. Does this happen @smailer?

I don't know how it works, sometimes when I upvote some posts, earning author amount will decrease.
Sometime increase, and I have no idea why.
I have a very slow vote power to make significant changes. But when earnings lowering happen this can be notably.