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I also don't understand this process yet

Everyone's vote carries a different amount of weight based on the amount of steem power you have. The more you have, the more your vote rewards the poster. If you downvote or flag a post, you'll decrease the value of the post in the same way.

but i didnt downvote, i was going to upvote lots of people but on some the $price went up on others down but i upvoted everyone

Someone better versed will have to explain this better.. but a logical answer would be that your steem power is low enough to drag the overall average down for the post. Since collectively there is less steem power/vote behind the post, the value goes down.

Or other people are downvoting that same post in the time it takes you to refresh the page.