A little too fast on the reply there, Glenn.
Spring rate is measured in Newton/mm. 58 N/mm in this case.
I'm at 235 lbs (105 kg) in the skin, I'm running 62 N/mm on my FSE450. I would guess 215 lbs and 58 on an FSE would be spot on for woods riding. On an EC/DE I would look at 54-56 for woods.
Look through the threads in the suspension section. This has been discussed a lot.