They are extremely accurate actually.
I seem to recall mine was Diesel B but not 100% sure now.
Have another read of the manual and follow the steps, you should only have to set it up once.
Mine was within 1 KPH for speed (against GPS) and within +/- 2 litres over 140 litres per fillup (long range plus sub) unless I was going real hard off road or on the beach when a small error would creep in due to the DP Chip fooling the ECU