You get HIVE returned after 3.5 days. The amount depends on the HBD you received and the average (median) price of HIVE over the next 3.5 days. So if you received 20 HBD, deposited 50 HIVE, and the average price of HIVE over the next 3.5 days is $1, you will receive 29 HIVE back (20 to pay for the HBD received and 1 HIVE charged as 5% fee).