I took the index in the words, converted the number to binary, added 3 zeros, calculated the sha256 digest, took the first Portion of the hexadecimal to transform it to binary, additional three zeros to your 8 digits in the binary and bought 00000010011 which translates to 19 in decimal. https://digibookmarks.com/story18821495/5-essential-elements-for-bip39-explained