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 2³² - 1 and the change index can be either 0 or 1.
Therefore, you can generate 2³³ 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.