This time I have made a simple table which calculates the % of SBD/STEEM that should be printed.
I think I'll need a few more calculations to conclude this spreadsheet. It is not going to be a sophisticated thing however I hope that it becomes good enough to have a full picture of the landscape.

Big effort brother, go ahead very useful what you do.
Hi jadams2k18!
The spreadsheet is to calculate the % of SBD/STEEm that is printed (created). for example, there are $5000 to be distributed as rewards: 50% is distributed as SP and the remaining 50% is distributed as STeem or SBD, depending on the debt ratio.
As far as I know, post's rewards depend on votes and the weight of the vote. You get 50% as SP and the remaining 50% as SBD or STEEM as mentioned above.
Rewards come from inflation
Every time a block is created, steem is created too. New steem are distributed to witnesses, authors and curators (or bots, jajaa)
I've never really been interested in knowing where they came from til now
This is from the blue paper:
This means that there is a fixed amount of STEEM to be created up to 20 years from now. And most of it is for rewards. Nice!
The amount that you see is an estimation in terms of SBD and changes daily.
I think i made a mistake. According to this article, what you see in your post is not SBD but STU (Steem tokens units). There is detailed explanation in that post.