I took the index of your words, converted the range to binary, included a few zeros, calculated the sha256 digest, took the main Portion of the hexadecimal to convert it to binary, included 3 zeros towards the 8 digits with the binary and obtained 00000010011 which interprets to 19 in https://bookmarklinking.com/story4978431/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39