For words that only have 3 letters, there isn't any 4th letter. Such as with the word “insert”, there aren't any additional letters afterwards and therefore should be the word "increase". The word “addict” is while in the BIP39 wordlist but you might have applied “addi” for “addict”. Artwork is https://socialimarketing.com/story4396246/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator