Why do the number of votes change when you reload a page?

It's a not-so-clever ploy to thwart potential cheaters by obfuscating the exact number of votes a post has. If the number of votes changes on a cheater's submission, they won't know whether that's due to their methods working or reddit throwing phantom votes their way.
See further explanation by /u/jedberg here and /u/ketralnis here.

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