I took the index with the words, converted the quantity to binary, included three zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to convert it to binary, extra 3 zeros to your 8 digits of the binary and bought 00000010011 which translates to 19 in decimal. https://natural-bookmark.com/story18826118/not-known-factual-statements-about-bip39-explained