I took the index from the words, converted the quantity to binary, added three zeros, calculated the sha256 digest, took the main Element of the hexadecimal to transform it to binary, included 3 zeros to your eight digits with the binary and obtained 00000010011 which translates to 19 in decimal. https://bookmarkingdelta.com/story18770804/not-known-facts-about-bip39-english-words