That is so, which is why I mean to use
Save to Disk (I previously wrote "send to file", my mistake) on Calibre and then manually copy the files to the device using CS, since downloading the whole library for the first time from CS takes forever, etc.
That's why I need to figure out a regular expression that would produce the files from Calibre with the naming convention used (but not documented) by CS, just so after transferring the files to the device CS would recognize them as downloaded on the device: available for reading on the device.
This is just for the first installation of my (large) library on the device using CS, because downloading takes up to much time. After that, I'll be using Calibre Content Server to download the files (a few at a time, as I incrementally add then to my Calibre library) from CS.
Maybe I am not making too much sense...