Its because the wallet you created using the New MEW interface is an HD wallet ( Hierarchical Deterministic Wallet). In a layman's language this type of wallet has so many addresses in it that can all be recovered using the same mnemonic phrase you have.
This kind of modern wallet implementation automatically generates an ordered tree-like structure of private/public addresses (or keys) using a single master seed key(This is what is represented as an easily readable 12 or 24 word Mnemonic Phrase)
This arrangement avoids us from going through the headache of having to back up each and every single private key of every address we have when all we have to do is just back up the mnemonic phrase representing lots and lots of addresses we own.
It also helps improve our transaction privacy as we can easily generate a new address we would love to use any time we want without having to worry backing it up
So you don't have to worry if you try restoring the wallet and you see a new address.
If you have some balance of tokens or Ether in you wallet, as you are trying to restore it. You will be able to see those addresses listed at the top
For example when using the My Crypto software wallet for my computer( you can also use any other wallet that supports HD wallet arrangement as listed below)
When i attempt to recover my wallet using my mnemonic phrase. All i have is to click on chose address
An then a list of addresses i would love to use pops up. Here i can select the address i wan to restore.
As you can see, the address with some Ether is at the top
All you have to do is check the wallet address you want to use and the click on unlock and you are good to go
If you want to keep recovering a specific wallet address then you will have to backup it's specific private key when the wallet is unlocked
Wallets that support Ethereum HD wallet arrangement.
Please be mindful of the number of word back up phrases they support
- myetherwallet (New and old interface)(supports even 24 word seed phrases)
- My Crypto Wallet (supports even 24 word seed phrases)
- MEW connect (supports even 24 word seed phrases)
- Exodus software wallet (supports only 12 word seed phrases)
- Parity Feather wallet- Light client (supports even 24 seed phrases)
- Atomic software wallet (supports only 12 word seed phrases)
- Trust wallet (supports even 24 word seed phrases)
- Jaxx Liberty wallet (supports only 12 word seed phrases)
- imToken (supports even 24 word seed phrases)
Caution1.
Always double check the links you use and download wallet software only from official wallet websites2.
Always create and restore wallets when your device is not connected to the internetIf you are interested in learning more about HD wallets
1.
https://www.investopedia.com/terms/h/hd-wallet-hierarchical-deterministic-wallet.asp2.
https://coinsutra.com/hd-wallets-deterministic-wallet3.
https://www.reddit.com/r/Bitcoin/comments/2zctw9/hd_wallets_vs_classic_wallets4.
https://coinrivet.com/hd-wallets-explained/