Steem Dollars DECREASING?

HI!

Fellow Steemsters, I hope you can help.

Why would one's amount of Steem Dollars DECREASE on a post?

I initially had 24 dollars on my first ever post on Steemit:

https://steemit.com/newbie/@grahnite/hello-to-the-world-of-steem

Now it is only more than 18 dollars?

Thanks for your help!