I took the index from the words, transformed the number to binary, extra three zeros, calculated the sha256 digest, took the primary part of the hexadecimal to transform it to binary, included three zeros on the 8 digits of your binary and received 00000010011 which translates to 19 in decimal. https://socialioapp.com/story4308433/bip39-seed-phrase-mnemonics-generator-an-overview