I took the index of your words, converted the quantity to binary, additional 3 zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to transform it to binary, extra 3 zeros on the eight digits of your binary and received 00000010011 which translates to 19 in decimal. https://livebackpage.com/story4365060/not-known-factual-statements-about-bip39-explained