I have no idea how it was determined. I can thank my ancestors for documenting it. I know we have family trees going way back but I have no idea how it's verified and quantified. But I have official national Indian cards showing membership and blood quantum. Its kind of screwed up tho my wife is almost full blood but less benefits (huge tribe)....and i am basically normal white dude with great benefits (small tribe)...How do you show 1/256 and how do they count it? Serious question.