Here ya go folks!!! Bless
As far as how they measure the THC percentage i would infer that they do it just like any other natural products extraction. They simply measure the mass of the sample of dried cannabis and then chop it as fine as possible, maybe grind with mortal and pestal, and dissolve in a solvent that is known to dissolve their target molecules such as diethtyl ether in the case of THC. There would probably be several "washings to increase the amount of thc dissolved out. The sample of either would then be, depending on the lab be injected into some sort of Gas Chromatograph, High Preformance Liquid Chromotography, or Mass Spec instrument, or one that is a combo of a couple of those such as a GC-MS. The GC and HPLC would seperate the several chemicals and they would be eluted at different times in peaks of various sizes related to the amount of each in the sample. From here quantative analysis would allow one to calculate the amount of each compound in the sample, and give you a percentage.
Chem 4's great weed.
It's not as good as the Chem "D",imo,and isn't as easy to get stellar results from,either.
It does yield a bit more,and finishes a bit later,near 70 days,give/take.
Cheers!
she keeps going and going and going...........