Every Steem account has a dynamic voting power value allocated to it by the blockchain to allow it to vote or decide on who the daily rewards go to and how much. Every day, new STEEM tokens are created to reward people bringing the most value to the Steem ecosystem (as decided by the community) and every Steem account can decide how these rewards are distributed by upvoting posts made by other Steem account holders. The final result is a daily allocation of rewards distributed through what is called the “Proof-of-Brain” mechanism. Learn more about this from the Steem.io website.
To bring finality to votes, the Steem blockchain limits the amounts of votes that any Steem account can make and this is implemented through the voting power mechanism. Every time an account votes on a post, its voting power decreases. The less the voting power, the less influence the account has with its votes. The voting power replenishes back to 100% over time though.
To make sure that its votes are cast in an efficient and fair way, the Utopian bot votes in ways that do not deplete its voting power down to uselessness. That’s why the bot starts voting on contributions at specific times when its voting power is at 100%.