Have you discussed this issue with Nikon? I do not believe we are going to be able to help you on this one. The camera meter, as has been said, has a certain range and the info in the viewfinder will show LOW just to warn the operator that a low shutter speed will require some firm support to take the picture or the use of flash. Nobody here can tell you why Nikon decided to use LOW instead of the actual low shutter speed.
Read the instructions manual, it is all there and now that you know what LOW means, steady that camera on a tripod and keep on shooting.