OldMedUser
Formerly Known as LabRat
That makes sense as that would be around a 13% strain.
You have to remember that cannabis has over 60 different cannabinoids so when you make something like RSO there's a lot more than THC in it. You can only make a very rough estimate of how much THC will be in each dose unless the oil is sent to a certified lab to have not only the potency tested but which cannabinoids are present and in what quantities.
For small batches $60 for the test is too much but if making an oz or more of oil in one batch then it can be worth the cost.