I played around for a few minutes earlier, and couldn't exactly reproduce that projected number, so I'm not sure what that represents.

I am pretty sure that the actual debt ratio from the blockchain perspective never goes above 10%, though. When it hits 10%, the median price is locked in a way that reduces the SBD price for internal conversions in order to prevent the debt from spiraling out of control.

The external market price doesn’t matter, because that's not the price that the blockchain uses when converting from SBD to STEEM (i.e. retiring the debt). The details are in the conversation with @moecki in the comments of the link that I pasted above. (I am on my cell phone right now, so can't chase them down again atm.)