Once your mix has been recorded, the unit creates a stereo master of your mix on the SD card. It is in the folder that has the same name as your song. You will see the file as 'songname.wav'.
Unless you need to tweak this stereo master .wav file in 'Master' mode, you're done. You only need 'Master' mode to play the song back on the unit.
If you decide to 'master' your final stereo mix by tweaking it with EQ, Compression or Dithering, or need to Normalize it, when you press 'record' the unit backs up your stereo master 'song name.wav' as 'songname_z.wav' and creates a new, tweaked 'songname.wav'.
FWIW, the engineers that designed the dp24/32 did a great job incorporating in a compact unit most of the features of a dedicated mixing console . The technical writers have failed to produce an owners manual that describes adequately, or gives good examples of how to implement, the well thought out features of the unit. I'm a retired recording engineer and studio owner. I've scratched my head more than once reading the manual. I can only imagine how frustrating it must be for people just starting out to make sense of it once past the basics.