I took the index from the words, transformed the quantity to binary, extra 3 zeros, calculated the sha256 digest, took the primary part of the hexadecimal to convert it to binary, added three zeros to your eight digits in the binary and acquired 00000010011 which translates to 19 in decimal. https://top10bookmark.com/story18779596/not-known-factual-statements-about-bip39-explained