Nikon D6 Reference Manual page 870

b: Metering/Exposure
b1: ISO Sensitivity Step Value
Select the increments used when making adjustments to ISO
sensitivity. If the value currently selected for ISO sensitivity is not
available at the chosen setting, ISO sensitivity will be set to the
nearest available value.
b2: EV Steps for Exposure Cntrl
Select the increments used for adjustments to shutter speed,
aperture, and bracketing.
b3: Exp./Flash Comp. Step Value
Select the increments used when making adjustments to
exposure and flash compensation.
818 A Custom Settings: Fine-Tuning Camera Settings
G button U A Custom Settings menu
G button U A Custom Settings menu
G button U A Custom Settings menu