How macro is the nikon 40mm f/2.8 lens really?

Here is the lens I'm talking about:
http://www.amazon.com/...B005C50H2Y
It supposively focuses at 6 inches, but I tested my 18-55 mm kit lens at 40 mm and it seems to focus around 6 in from the subject as well, but in no ways do I see it as a micro lens. How could this lens be macro if it focuses at the same focal length that my kit lens does?

I know it is probably irrelevant, but I have a nikon d3100.

I think you misunderstand what a macro lens is.

It is a special flat filed lens that can shoot image to subject ratios of 1:1, 1:2, 1:3 and 1:4.

How close the camera/lens is from the subject has to do with the focal length of the lens. A 105 mm lens will be much further away from the subject than a 40 mm, yet they can each shoot macro at 1:1 ratios. That distance is called the lenses standoff distance.

The 18-55mm kit lens focuses to a minimum distance of 11" or 28cm. At 6" from the subject, the resulting picture will be blurred. The minimum focusing distance of the 40mm macro is 6.4" or 16.26cm. That's a bit more than half the distance of the kit lens.

http://www.bhphotovideo.com/...ED_II.html
http://www.bhphotovideo.com/..._AF_S.html

Macro is macro only if it captures an object in at least it's original size if not bigger on the recording medium. So in film, an ant that measures 3mm long will be 3mm long also on film. Printing the image on that frame of film will produce a very large magnification of that 3mm ant. The principle is the same with digital.

The minimum reproduction ratio is 1:1 and works relatively for minuscule objects. Close distance focusing is critical. Only macro lenses can get to as close as 6 inches, with some setups even much closer. Longer focal length macros work the same way and if compared to regular lenses of the same focal length, they can focus far much closer to the subject.