I took the index from the words, converted the number to binary, extra 3 zeros, calculated the sha256 digest, took the first Element of the hexadecimal to convert it to binary, additional three zeros to your eight digits on the binary and bought 00000010011 which translates to 19 in decimal. https://sociallweb.com/story4238184/an-unbiased-view-of-bip39-seed-phrase-github