I took the index on the words, transformed the range to binary, extra a few zeros, calculated the sha256 digest, took the main Component of the hexadecimal to transform it to binary, extra 3 zeros on the 8 digits of the binary and received 00000010011 which translates to 19 in https://cheapbookmarking.com/story19521549/the-2-minute-rule-for-bip39-all-words