I took the index from the words, converted the quantity to binary, included a few zeros, calculated the sha256 digest, took the main A part of the hexadecimal to transform it to binary, additional 3 zeros for the 8 digits with the binary and received 00000010011 which translates to 19 https://moodjhomedia.com/story2599739/a-review-of-bip39-phrase-list