From your post:
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There is no perfect time for voting a post, sometimes it may be the 14th minute, sometimes a bit earlier or later. It depends on when the 'big one' will hit the target.
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This explains why I have different curation awards when the post reward is of a similar value. It all depends when a large curation vote is placed relatively to my vote time.
Thanks for explaining this - one of Steem's mysteries solved. Also, thanks for improving the readability of the curation table and giving it a sort option.