This is due to hierarchical derivation, which essentially defines many different ways of generating a private key from a seed phrase.

For example, given a seed phrase like `immense soup feed arrest erupt arrow little nephew regular trap radio danger`, which `solana-keygen` gives a pubkey of `jtFuWc4r1Y6UNuU13LngguXuyozapVnRVfnv9VwqWKr`, you can do:

```
solana-keygen pubkey prompt://?key=0/1
<Paste the words here>
EqqwJANhbtzB2bwFv7N4wEQA8fj3hxAJsoq7iE9szEN8
```

Or

```
solana-keygen pubkey prompt://?full-path=m/44/2017/0/1
<Paste the words here>
97oZZGsDN5nobMDsk4XDhPHjExxqAS5ehfFRUAyBNHEF
```

Depending on your derivation path, you'll different private keys.

More information in the Solana docs at https://docs.solana.com/wallet-guide/paper-wallet#hierarchical-derivation