For words that only have three letters, there's no 4th letter. Such as with the word “insert”, there are no much more letters Later on and thus must be the word "increase". The word “addict” is while in the BIP39 wordlist however, you would've applied “addi” for “addict”. You may https://sb-bookmarking.com/story18972134/an-unbiased-view-of-bip39-seed-phrase-github