I took the index with the words, transformed the amount to binary, included three zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to transform it to binary, added three zeros on the 8 digits in the binary and obtained 00000010011 which interprets to 19 in decimal. https://dmozbookmark.com/story19631602/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting