this is true, but this debt is secured debt. Its secured by the same steem that gives steem power. SO when they say its s a debt instrument, think of it like a check (which is also a debt instrument). If you have $50 SBD, all that really is is a check written for $50 worth of steem.
So lets say you get paid $100 for a post. As youre probably already aware, you get $50 in steem power and $50 sbd.
When you get that $50 worth of steem power, the miners create $500 worth of steem. This goes into the vesting fund, which is like a big box that holds all the steem power. This is the "checking account" that your SBD check is written on. So in the same way you would make a deposit to your checking account when you write a check, the steem blockchain makes a deposit to their vesting fund to make sure they have enough money on hand to cover your check should you elect to cash it.
That 500 partially pays for the additional SP they gave you (50 steem) the rest goes to SP incentives (thats why your SP balance increases even when you do nothing). But the part that goes to SP incentives also goes to "back" this SBD debt.
When you use the convert SBD function in the UI, what happens is that the debt insturment (the steem dollars) is destroyed, and you are given steem from the vesting fund in return.
Thanks for the deeper clarification of the matter. I can't do the math on this matter. But considering what is written in white paper under a section of Sustainable Debt to Ownership Ratios says: "For every SMD Steem creates, $19.00 of STEEM is also created and converted to SP.". Following on that I would do numbers differently than you, but it doesn't even matter what exact numbers are in question.
I believe your numbers are right or excellent for an explanation.
I was just interested to see some knowledgeable answer on that field and you explained with numbers how steem(in SP) and steem dollars are created for a user that receives them and what it means for the platform.
Last part about the conversion of SBD in UI was also something new thus really helpful.
It's very different from other cryptocurrencies in that matter since others operate on transferring "real" value and not creation of new value. People generally don't get how something gets value and don't get where money does comes from (@hisnameisollie explained that in the last post on this topic) but this part on creation is also very important IMHO, because it gives people real money they can take out immediately unlike vests.
The way they come up with the numbers is very counter intuitive (and also not the way i would do them)
So you make $50 SBD and $50 steem power for a blog, for a total of $100
they take $1000 and put it in the vesting fund.
$50 of that is to pay for your new steem power. The other $950 of that is the 19/1 DTO backing that theyre talking about (950:50 = 19:1)
see numbers 'R' fun!