You might want to look up the landing distance tables contained in QRH which can be found in the link you provided.
I did and get the following figures which all make perfect sense.
Weight 66Tons Autobrake Low, No Rev
Dry Ref Dist = 1950m Correction -10m/Ton below 66Tons.
Good Medium Ref Dist = 1960m Correction -10m/Ton below 66Tons.
Medium Ref Dist = 2140m Correction -20m/Ton below 66Tons.
Poor Ref Dist = 3540m Correction -30m/Ton below 66Tons.
The bigger corrections / Ton below 66 Tons for Medium - Poor conditions will be due to Airframe drag etc. which has a longer time to produce an effect due to the longer Landing Distance.
I suspect your figures have a printing error.