For words that have only 3 letters, there is no 4th letter. Such as with the word “increase”, there won't be any a lot more letters Later on and thus have to be the word "increase". The word “addict” is during the BIP39 wordlist but you might have used “addi” https://bookmark-master.com/story18862144/considerations-to-know-about-bip39-seed-phrase-generator