A portion of the reward on a post goes to curation rewards, that is split between the upvotes accordingly to when you vote, probably more reward being in the middle, but its complicated math and it varies for hive versus each tribe...
But you can try it in practice, when you have LASSECASH POWER (you just got 600 LASSECASH on your first comment, see it here:
https://www.lassecash.com/hive-174578/@pele23/to-selfvote-or-not-to-selfvote )
By upvoting before me and look in your wallet/account how much you made after 7 days.