Revit :: Format Of Surface Element

I am exporting gbXML file from Revit Architecture 2013. And I am looking at the format of the name of the surface element. According to the Autodesk wikihelp, I understand that it is composed in a form as : orientation-space-(other space)-exposure-type-sequence number-(opening type)
 
It means if the surface is an interior wall surface, there will be two adjacent space names recored here. such as N-101-102-E-W-D-84 
 
But I notice that in my gbXML file, I have some terms like :  B-2-2-I-F-10, B-2-2-I-F-16, X-1-1-I-O-6, and  X-1-1-I-O-15,  I notice that when the orientation is "Bottom" or it is a type of "air", the space names will repeated twice.