I took the index from the words, transformed the range to binary, extra 3 zeros, calculated the sha256 digest, took the first Component of the hexadecimal to transform it to binary, added 3 zeros to the 8 digits of your binary and received 00000010011 which interprets to 19 in decimal. https://greatbookmarking.com/story18880549/bip39-phrase-generator-can-be-fun-for-anyone