Not sure on the red dot displays but the white dot ones also do it based on WHEEL SPEED MPH (which is the ACTUAL speed - Speedo overreads by about 4-8mph depending on your Speed Impulse number on VCDS).
For example mine will show cruise control at 30, dial would be 30, MFD speed readout be 26.
Ergo if you timed Rich's 0-60 on a video camera it would be ever so slightly quicker, the time it takes to pull the extra 4-8mph.