Assume that you have a wallet with standard derivaion path of m/44'/0'/0'.
Your addresses are generated at m/44'/0'/0'/x/y in which x is the change index and y is the address index.
The address index can be from 0 to 2
32 - 1 and the change index can be either 0 or 1.
Therefore, you can generate 2
33 addresses at the derivation path of m/44'/0'/0'.
You can also change the account index and have more addresses generated from the same seed phrase. For example, you can generate a completely different wallet at the derivation path of m/44'/0'/1'.
(The account index can be from 0 to 2
32 - 1.)
So, with changing the account index, the change index and the address index, you can generate 2^65 addresses from a single seed phrase and you can still generate more addresses with using non-standard derivation paths.
According to mastering text book there is a possibility of like 4 billion child addresses possible of been generated from one seed phrase as per limit in the HD wallets formats (232-1) from each parent extended keys.
A single seed phrase can generate much more addresses.
You can generate 4 billion addresses (4,294,967,296 addresses to be accurate) only with changing the address index.