I took the index with the words, transformed the number to binary, additional a few zeros, calculated the sha256 digest, took the first part of the hexadecimal to convert it to binary, added a few zeros into the 8 digits on the binary and received 00000010011 which interprets to 19 https://kingslists.com/story20170341/bip39-seed-phrase-mnemonics-generator-an-overview