This
is just a case of reading the table right and applying a bit of interpolation.
Enter
top row as this is the speed you're at, with a weight of 48000kg at 90 mins you're going to be between 590-580 nm.
Interpolation
shows that at each 1000kg in weight is proportional to 2nm.
The
answer spread is good enough to not have to interpolate in any depth.