Nematology labs are notorious for using different units of soil. Some labs will send results per gram of soil or per gram of roots for certain nematodes other than soybean cyst nematode. If you are looking at results from one lab and recommendations from another source make sure the units agree or that you do the math to convert to the same units. Check to see how the SCN level is measured. The University of Missouri and most University labs located at land grant institutions throughout the Midwest report SCN levels as egg counts.
Some labs report eggs and juveniles.
There are labs that do a variation of this and report cysts and estimated eggs. There are several ways a lab can go from cyst counts to estimated eggs. One way is to count cysts and crush a representative numbers of cysts. There are some labs that pick an average number and multiply the number of cysts by this average number of eggs per cyst. The number of eggs in a cyst is reflective of the host status of the plant, the environmental conditions and the age of the cyst.