The D300 has an indicated base sensitivity of ISO 200, sensitivities below this (ISO 160, 125 and 100) are indicated as L0.3, L0.7 and L1.0 respectively. The same is true above ISO 3200 with ISO 6400 indicated as H1.0. the compromise at ISO 100 is highlight range which falls just over two thirds of a stop (0.7 EV) short of the highlight range seen from ISO 200 upwards.