The math of blood quantum is straight-forward.

Suppose a tribe has 1,000 enrolled citizens. Let’s assume they are all full-blood for starters, but half the children born are mixed – their other parent either from another tribe or non-Native. Continuing this, after seven generations, 2% will be full-blood, 9% will be half, 23% will be quarter, 31% will be 1/8th, 23% will be 1/16th, and 11% will be less than that. You can see where this going. By the eighth generation, half the tribe will be less than 1/8th. It’s a recipe for what the white man called “extermination.”