Getting a key size of DSA/Elgamal certificate
It's extremely likely that 1024 is the master key size as authentication and signing are usually the main purposes of PGP. The key used for encryption is generally valid for a shorter time and is therefore a subkey of the master key. So both 1024 and 2048 bit public keys are included in the PGP certificate.

Note that the key size for encoding the key will be larger and the key strength (compared to e.g. an AES key) will be much less.

Both 1024 and 2048 bit keys are rather small for common purposes. It is highly advisable to upgrade to larger, RSA based keys. For more information about key sizes and their strengths, please take a look at https://keylength.com.