I took the index on the words, converted the range to binary, included a few zeros, calculated the sha256 digest, took the first A part of the hexadecimal to convert it to binary, extra 3 zeros on the 8 digits of your binary and got 00000010011 which interprets to 19 https://loanbookmark.com/story18982238/the-5-second-trick-for-ledger-seed-phrase-bip39