I took the index with the words, transformed the range to binary, extra a few zeros, calculated the sha256 digest, took the 1st Component of the hexadecimal to transform it to binary, extra three zeros for the eight digits of the binary and obtained 00000010011 which interprets to 19 in https://keybookmarks.com/story19181510/ledger-seed-phrase-bip39-no-further-a-mystery