I'm thinking about ordering the Birkenstock Milano Nubuck Sandals - Cocoa 45 M EU - which is this sandal.  However, I'm having a very hard time figuring out what the 45 M EU means.  My size converted would be 37 (6-1/2 US), but does this description mean that there is only one size available??? (45 M EU ???).  I tried the Help screen, but they didn't know.