For words that only have three letters, there is not any 4th letter. For example with the word “increase”, there isn't any more letters Later on and therefore must be the word "increase". The word “addict” is from the BIP39 wordlist but you would've used “addi” for “addict”. BIP39 and https://bookmarkfox.com/story4576578/the-ultimate-guide-to-bip39-seed-phrase-mnemonics-generator