[Borgbackup] Interpreting the progress bar

[Stan Armstrong]

Is the progress indicator (processing files) interpreted somewhere?

Here is a snapshot of one of mine:

processing files
93.93 GB O 93.93 GB C 25.58 GB D 28258 N 
media/2TB-1/Down...rnity_1.4.0.6.tar.gz

"N" appears to be the full pathname of the current file being processed.

The first and second entries change quickly, with number of GB remaining 
almost identical. the second entry increases by 0.01GB a fraction of a 
second before the first entry does. What does "O" mean?

"C" sometimes increments in step with the first two entries, but it 
doesn't quite keep up. What is it?

"D" changes very slowly. What is it?

Thanks,

Stan