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They do, but the 25% is distributed amongst the voters based on this algorithm:
Current voting algarithm.png

So does that means, if someone upvotes after 27 minutes ( first upvote), then the author gets only 10% even though the post can reach high afterwards ?

And if its done after 30 mins, then the author does not get anything ?

This refers to the curation reward @sanjeevm
100% of a post
75% authour
25% curator
at posting, 100% of curation reward to authour, 100% of the 25% of the
post, the curation reward.