When you want a Bitcoin/Ethereum/XRP or any other of the supported cryptocurrencies, which at the time of writing are 24 in total, the device will bring up the wallets that are generated from the seed. You don’t add your own wallet, you don’t change the wallets. The wallets are determined from the seed.

A given mnemonic seed will 𝗮𝗹𝘄𝗮𝘆𝘀 generate the same wallets. Your mnemonic is your one and only secret.

You might be wondering what are the odds of someone getting their random mnemonic key and, since they will always derive the same wallets, granting them access to all your funds. BIP39 has a wordlist of 2048 words from which it chooses 24, with or without repeats, contrary to what you might expect, it’s not 2048²⁴ but rather 2²⁵⁶ which is:

one in 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936 combinations

To put this into perspective I tried making a nice chart but there are no relatable events I could use to compare it with that could be represented together. But let's just say that the odds of winning the Powerball, are 1 in 292,201,338 and the number of atoms in the whole planet is 1.33E50 which is 8,706,172,122,999,999,466,307,584 times smaller than the number of combinations available. Let’s just let that sink.

There are eight septillion, seven hundred six sextillion, one hundred seventy-two quintillion, one hundred twenty-two quadrillion, nine hundred ninety-nine trillion, nine hundred ninety-nine billion, four hundred sixty-six million, three hundred seven thousand, five hundred eighty-four times more valid combinations of 24 words from the 2048 word list than atoms in our planet.

I’m going to pretend this made it easier to understand, but if you want my tl;dr version of what I just said, the odds of running into any issues are not zero, but so close to zero you shouldn’t have to worry about that.

The coins are not inside the device, if you lose the device you don’t lose the coins, you lose… well, the device. It might be difficult to understand this concept for some people, you get a fancy device that is called a wallet, a physical wallet, yet it holds no coins. Remember what I said a couple paragraphs back? It holds your mnemonic, your one and only key.

The problem comes when you lose the device and the seed. If you only lose the seed, you can send your coins to another set of wallets, if you only lose the device, you can restore your wallets on a new one from the seed.

Lose both, gameover.