I'll respond as someone who has seen this happen. If the respondent has 10 full blooded in his 3 greats ancestry of 32 (2^5), would that not be 1/3rd ancestry?
Of course, Harvard Professor Elizabeth Warren, is only claiming a single 1 of 32 ancestors as being 'red', maybe high cheekbones meant political proclivity?
Not really. Sort of close, but not exactly. It’s 10/32 or 5/16.