I took the index of your words, converted the range to binary, added 3 zeros, calculated the sha256 digest, took the main Portion of the hexadecimal to transform it to binary, added 3 zeros on the 8 digits on the binary and bought 00000010011 which translates to 19 in decimal. https://pr1bookmarks.com/story19251295/not-known-factual-statements-about-bip39-explained