The check-in process is a little difficult to understand. Also, the listing does mention it, but note that there is no air conditioning, so it was very hot when trying to sleep (we stayed here the last week in May). Otherwise, our stay was great. The room was as advertised and location was pretty good (about a 25 minute walk to the city center).
For check-in, make sure you get the code from Laura before you get there. When you enter the code in the gray box, the keys are in that gray box. You then use those keys to enter the door from the street, walk up the first half flight of stairs, then open the mailbox at the top of the first half flight of stairs (and make sure you ask Laura which mailbox it is). Then, make sure you get the right set of keys for your unit. Ask Laura which unit it is, then make sure you pick the correct room (the names are on each door).