We booked one night at this accommodation. The most difficult thing was finding the building and here is why after looking for 1.5h, we realized there is no visible sign of this building or hostel from that street but a tiny plaque next to the door entrance. Google map took us exactly to Via Porta Rossa (which is great). We did ask three people at different stores who were working on that same street.
In addition to this, after few blocks, the sequence jumps from 7 to 19 and on, so you may get a sense you are kinda lost.
I classify this accommodation as an apartment for rent, more than a hostel. It is inside a residential building and our room was on top floor so we went up stairs with luggage. There is no receptionist available and the host left after handling the key and explaining the usual things, so we were by our own mostly.