You've got two options in the KOMBI module.
BC_DIGITAL_V_KORREKTUR - which obviously corrects the digital readout, and
BC_V_KORREKTUR - for the speedo.
That said, I've not actually tried it. I like the over read as default with the option of looking at the real speed on the digital display. It's bloody accurate too, always bang on with my TomTom.
MY14 Space Grey F11 530d M-Sport