I took the index on the words, transformed the selection to binary, included a few zeros, calculated the sha256 digest, took the first Section of the hexadecimal to convert it to binary, included three zeros on the eight digits on the binary and got 00000010011 which interprets to 19 in https://isocialfans.com/story4266935/an-unbiased-view-of-bip39-seed-phrase-github