Built-in codes as exactly that, built-in. They're not built into the software, but the Pronto itself. The 8000 "codes" are nothing more than a reference or label indicating what built-in IR sequence is used.

If you load a CCF that someone made from learned signals then you'd see 0000, 0100, 900X, etc. format hex. These sequences can be broken down into timing information which describes the IR pulses.

You can also derive protocol and function numbers from them using decoders such as John Fine's DecodeIR.dll (used with third-party programs). With the protocol and function number in hand, you can regenerate absolutely clean (Pronto Hex) codes using John's Makehex program and a corresponding IRP file.

Bruno