Why two readings on folder size
 

Size: 346 MB (363,177,253 bytes)

Size on disk: 848 MB (889,651,200 bytes)

Does the folder contain lots of little files?

Contains: 20,470 files, 1,406 folders

There's your answer. You've got a lot of slack space. Disk space isn't allocated down the bit, its allocated in clusters (often between 1k to 32k in size). That means that even if you have a file that is smaller than your cluster size, the remainder of the cluster is unusable. For large files this isn't a problem as they'll fill several clusters competely and the last cluster partially. For small files, this can lead to very inefficient use of the disk.

If this is a problem, you might want to consider tar'ing/zipping the files or changing your file system around to use smaller clusters.

I assumed that was the reason but did not know for sure.

Another question when you upload to a server which would apply to allocated disk storage.

Size: 346 or
Size on disk: 848

Any answers to my last question?

it depends on the default allocation size. NTFS for example is 8KB, so even if you create a 1 Byte file, it will fill up 8KB. I dunno what *nix OSs have though.

LOL, for a retired adult webmaster you sure know a lot about computers :)