This gives a look at it. The actual supply of Hive, and then if all HBD was converted to Hive at current feed price of Hive. So if Hive was right now worth $1 equivalent, there would be about 510 million Hive in the total. The more HBD, the more debt, which is why if price dropped a huge amount, the haircut would take affect. Not sure how that would affect the HBD APR...