I took the index with the words, transformed the number to binary, extra a few zeros, calculated the sha256 digest, took the main A part of the hexadecimal to transform it to binary, included 3 zeros into the 8 digits from the binary and obtained 00000010011 which translates to 19 https://pr7bookmark.com/story19094856/bip39-phrase-generator-can-be-fun-for-anyone