What is it you are actually trying to work out?
Sag is often used to refer to how much the springs compress over time. It is also used for static (racing) sag, how much they compress from unloaded to loaded with the vehicle weight.
Rather than how much a spring sags, you should be looking at suspension droop and compression if you want any meaningful info regarding the way the vehicle is used.
You'll get many different answers, but I perosnally view extended travel more important than compressed travel for rock crawling.