I had read in a couple of blogs from 2 years ago that to avoid bots from automatically upvoting first to earn additional rewards that a 5 minute countdown had been designed. In the first minute there were no rewards but 20% of rewards were available each minute and at 5 minutes 100% of curation rewards were available. For example, if you voted with 4 minutes remaining then you could earn 80% of the curation rewards you would have earned by waiting 5 minutes. Again, this was a couple year old blogs but I couldn't find anything recent confirming if this was still the case.
!PIZZA