I'm in the market for a surface 3 and I'm confused by the model numbers for the surface configurations that are available. I have found model numbers 7G6-00001 and 7G6-00014 that have the same 4gb ram 128gb storage configuration and 7G5-00001 and 7G5-00015 that have the same 2gb ram 64gb storage configuration. Does anyone know the difference between these models? The only thing I can think of is that one of them comes with windows 10 preinstalled. Is this the case? Thanks!