Hi, Cletus. Please don’t ‘mess with’ those files. 
By default, there are three internal Backup folders. ‘Backup’ holds the most recent backup of the database, ‘Backup0’ the next most recent and ‘Backup1’ the oldest.
Each time ‘Backup & Optimize’ is run, the contents of ‘Backup’ are replaced with the most recent state of the database and the oldest state of the database is purged and replaced with the contents of the next most recent. I use the default 3 internal Backup folders. More would be overkill.
If something were to go wrong with the database (perhaps data corruption caused by a power failure or a forced quit while data is being written to disk), one can switch to an older state of the database by using Tools > Restore Backup. See the online Help at Help > DEVONthink Pro Help and search for ‘backup’.
Warning! Here comes my ‘belt and suspenders’ speech:
I don’t depend on scheduled backups. Periodically I will run Tools > Verify & Repair to assure myself of the integrity of the database. If errors are found and cannot be corrected (which hasn’t happened to me for some two years or so), I will run Tools > Restore Backup and check the integrity after swapping with the most recent previous state of the database.
I use a very convenient script that’s available in DT Pro and DTPO (but not for DT PE), DT Pro’s Scripts > Export > Backup Archive.
Whenever I’ve invested time and effort in modifying my database, at the next time I take a break I will invoke the Backup Archive script. This will first run the Verify & Repair and Backup & Optimize quality assurance and internal backup routines, then save a compressed and dated backup of my database at the location I’ve chosen on my drive or external medium.
It only takes a few seconds to invoke Backup Archive. When I return from my break, Backup Archive has done its job and the database is ready for work.
The result is that I’ve got a current backup both internally and externally. As a hard drive could fail at any time (unlikely, but true), it’s a good idea to copy or save the external backup to another computer, external drive or CD or DVD periodically. To access that external backup archive, double-click it to unzip it, then double-click on the resulting database file to open it under DT Pro.
I haven’t had to resort to a backup for more than two years. But my databases are much more valuable to me than the computers that host them. Keeping my backups current provides peace of mind.