The required collateral is twice the HBD amount divided by the lowest hourly feed price in the past 3.5 days before the conversion. This amount of HIVE is immediately deducted. At the end of the 3.5 days, the conversion cost is the HBD amount divided by the median feed price over the past 3.5 days. The difference between the required collateral amount and the conversion cost is returned.

EDIT: 5% fee is added