Hotel with 2 Ground floors??

Back in Copenhagen after 2 days in Malmo, Sweden. I checked into a different hotel (my fourth one in CPH) that was near the train station. I was given room #09. The elevator had a button labeled "S" which was the ground floor with the lobby. Just to the right of it was another button, also identically labeled "S". This was one floor up from the ground floor, and contained the "0" rooms (01 - 09) including my room. Above those were buttons 1 through 4 for the floors above that. This means that the floor labeled "1" was really floor 2 (Europeans start numbering floors with 0 for the ground floor), or floor 3 in American terms. Floor "S" was both floor 0 and floor 1 (floor 1 & 2 in American) I'm not sure what "S" stands for, but why have TWO "S" floors, especially when they are physically different floors. It's as if my floor, the zero rooms floor, was added later as an afterthought, and squeezed into a space between two existing floors. Something like the "floor 7½" in Being John Malkovich. Or maybe I just stepped into... the Twilight Zone??