#6. "RE: I guess this is the place to ask what is with low ISO settings on my D90" In response to In response to 0
As already noted, you have L0.3, L0.7, and L1.0 options. The reason Nikon doesn't use numbers is because these ISO levels are "fake"...in the sense that they're being created by reducing your highlight range.
All cameras have roughly 3 stops of highlight space above metered gray (about 12.7% gray.) When you shoot at the "L" ISO levels, your highlight space is reduced, so you may clip some highlights that you wouldn't have clipped at ISO 200.
The benefit of these ISO levels comes with scenes that are mostly dark, such as a sleeping black dog on a dark floor. Shooting at the "L" ISO levels reduces noise. In such a scene it's no problem to lose the highlight space, as there are no real highlights to speak of, and the improvement in shadow noise is noticeable.