Your accelerate stop distance will be less than calculated because your TAS will be less at the actual temperature than the TAS assumed at your FLEX temperature. The real figure will be about 3% less for every 10 degrees difference in temp.
Eg.
Calculated ASD with a flex of 60 gives 2500m
actual temp is 10 degrees
ASD is reduced by 3% x (60-10)/10 = 15% (so 375m)
actual ASD is 2500-375 = 2125m