Bip39 Checksum. Entropy values should be sourced from a powerful source of randomness. What this means is flipping a good coin, rolling a good dice, sound measurements etcetera. Never use phrases from guides, lyrics from music, your birthday or steet address, keyboard mashing, or everything you think that is random, https://robustdirectory.com/listings730236/bip39-standard-https-linktr-ee-bip39-the-2-minute-rule-for-bip39-compatible-wallet