An 18-word mnemonic phrase will increase security by including added words for the sequence. Here’s an case in point: Standard recovery phrases use a certain list of 2048 words next the BIP39 standard (Bitcoin Enhancement Proposal 39). You could validate if your words are A part of the BIP39 list https://bookmarkinglife.com/story4321564/the-5-second-trick-for-ledger-seed-phrase-bip39