EXPLAIN REWARDING PROCESS:

FOR INCTANCE:

- Last 24H's Blockchain gaining is 100%

- Blockchain gives 10% of 100%

If you write a good content on Steemit, and below the post you see 800SD the first time. So, it can reduce or increase. That based on Steem Power users. 

Why it reduces: When content better than you the people who have a high Steem Power UPVOTE the content get high rewarding so your post become affected.