I took the index from the words, transformed the amount to binary, included a few zeros, calculated the sha256 digest, took the 1st Element of the hexadecimal to convert it to binary, included 3 zeros to your 8 digits in the binary and acquired 00000010011 which interprets to 19 in https://kingslists.com/story20121627/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator