I took the index of your words, transformed the variety to binary, included 3 zeros, calculated the sha256 digest, took the first part of the hexadecimal to transform it to binary, added 3 zeros into the 8 digits with the binary and obtained 00000010011 which translates to 19 in decimal. https://socialbuzzmaster.com/story4615953/facts-about-bip39-seed-phrase-github-revealed