I took the index on the words, transformed the range to binary, included a few zeros, calculated the sha256 digest, took the main Element of the hexadecimal to transform it to binary, included a few zeros to your eight digits with the binary and got 00000010011 which interprets to 19 https://allkindsofsocial.com/story4189663/considerations-to-know-about-bip39-word-list-pdf