TBT if 30 year bond yields rise to 6%

Any idea on what the value TBT would rise to if the yield on 30 years bonds rose to 6%?

 

?.......If bond futures fell from ~130 down to ~100, a ~6% yield, that would be a ~23% decline. You might expect TBT to rally twice as much?....46%.

 

I read the prospectus and TBT is supposed to track *daily* moves 2:1. In that case, wouldn't this compound daily? Thus (not too) different outcome. ie up 1% per day for 20 days is not =+20%. Instead = 1.01 ^20. (22%)



How do these ETFs actually work anyway? Does heavy buying or selling increase/decrease the fund's position? Is it all automatic intraday, or is there a manager who balances things daily? etc... Same question goes for all of these derivative ETFs (whether SPY, or ultras).