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The payouts are coming from a pool. When new votes are cast for other posts your share is diluted. You only know how much you receive for a post when the payout happened, so all activity until July 4th will lower the amount under all other posts.

Ah that explains it, thanks :)

I have noticed this on some posts too. After a few days it seems to tick down around 1% every hour even with no vote changes.

Market cap changes can impact it too.

How come it's only happening on one of my posts? I've lost like $600 almost 10%, but my other post doesn't seem to have lost nearly 5%. What gives?

We obviously need more tutorials describing all this.

Each post has mostly a different set of voters. Those unigue voters Steam Power becomes less valuable as they vote for other post.