When I use SuperDuper to make a clone of my MacBook Pro 2017 15-in (macOS 10.14.6), in the resulting log, about five minutes after the copying begins, the following message occurs:
| 11:14:27 PM | Info | Ignoring
/private/var/audit/20150725033113.crash_recovery
The message repeats with a different 14-digit number about 2,500 (sic) times, then the time changes to 11:14:28 PM and repeats about 150 more times.
As an experiment in living dangerously, while logged in as root I went into that folder and found that I have a bunch of similarly named files. One of them appears to be a “current” file, but there aren’t files for every single day. There were maybe 50 or 60 files in total, although I didn’t actually count them. None of them were older than August, 2018, so maybe by default the files should be automatically deleted after 1 year and that isn’t happening for you. As a test, I highlighted all of the files from 2018, moved them to the trash and successfully emptied the trash. So far, nothing’s happened. My guess is that if SuperDuper ignores the files, and you can boot okay from a SuperDuper clone, they are files you don’t need.