Since we are integrated with Hostelworld, you have to set up one bed for one person, as Hostelworld (and Hostelbookers) operate with number of people.
Double room is "2". Therefore, you should look at the BedView and imagine
that you need one line per person and that these are not beds, but
simply people.
It doesn't change the way the system works. If you block/book one bed then entire room gets blocked.