Kindlegen errorlevel/exit code listing?

I'm writing a tool to automate calling Kindlegen in batch fashion. I'm seeing an ExitCode of 1 even though it succeeded (albeit with warnings). My understanding is that the normal rules on DOS/Windows are that any exit code/errorlevel > 0 should be an error.

Does anybody have a list of the non-standard exit codes used by kindlegen, so I can handle them appropriately?