I took the index on the words, converted the range to binary, additional a few zeros, calculated the sha256 digest, took the initial Element of the hexadecimal to transform it to binary, added 3 zeros to the 8 digits of the binary and received 00000010011 which translates to 19 in https://kingslists.com/story20048895/facts-about-bip39-seed-phrase-github-revealed