I took the index of the words, transformed the number to binary, added 3 zeros, calculated the sha256 digest, took the main Element of the hexadecimal to transform it to binary, included 3 zeros to your eight digits of your binary and received 00000010011 which translates to 19 in decimal. https://indexedbookmarks.com/story18839618/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39