For words that only have 3 letters, there's no 4th letter. One example is with the word “increase”, there are no much more letters afterwards and therefore needs to be the word "incorporate". The word “addict” is during the BIP39 wordlist but you might have applied “addi” for “addict”. To https://bookmarkalexa.com/story4308143/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator