I took the index from the words, transformed the number to binary, added three zeros, calculated the sha256 digest, took the first part of the hexadecimal to convert it to binary, added a few zeros to your eight digits from the binary and obtained 00000010011 which translates to 19 in https://ilovebookmarking.com/story18857208/the-definitive-guide-to-bip39-seed-phrase