+1 to what Arnie said, CST is industry standard and you don't have to be spot on at 400CST, it's just a guess based on my experience racing 4WD SCT in the past:
https://www.teknoforums.com/threads/build-review-sct410-3.1389/
*** Side note, not all manufactures are consistent with their...
Good Luck!
If I was going to race a Slash on dirt, I would start with 10-7-3 in the diffs and 400CST in the shocks then go from there.
Pretty good tuning guide here to help you make adjustments depending on what you want the truck to do...