I took the index of the words, converted the range to binary, added three zeros, calculated the sha256 digest, took the 1st A part of the hexadecimal to transform it to binary, included 3 zeros to the eight digits of your binary and received 00000010011 which interprets to 19 in https://bookmarkbirth.com/story18903424/ledger-seed-phrase-bip39-no-further-a-mystery