Hive account@lottobot is not guaranteed to upvote any post that is entered into its lottery. There is a chance that any post entered will win a 100% upvote, and that chance is reduced by the number of entrants in any given lottery. Hive account@lottobot could not upvote every post that enters it's lotteries (this would quickly deplete it's voting power). Instead, it selects randomly from among entrants and gives one of them a 100% upvote. You can read Hive account@lottobot's introductory post, where this process is explained in detail, here.

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