I took the index in the words, converted the number to binary, extra 3 zeros, calculated the sha256 digest, took the main Portion of the hexadecimal to convert it to binary, included three zeros to your 8 digits of your binary and obtained 00000010011 which interprets to 19 in decimal. https://freshbookmarking.com/story19006832/ledger-seed-phrase-bip39-no-further-a-mystery