As you can see, I have an external hard drive. The drive is contains 1 folder. The drive is at 211gb used, but the folder is at 187. There's no hidden files/etc.
The left window only reports the space that the files themselves take. On the right-hand side the filesystem overhead (metadata, journal) is included. 8400 files and 1700 directories imply a significant amount of metadata. Further, some filesystems like FAT32 do not merge multiple small files into one block/cluster, hence files smaller than the blocksize are going to waste some space. I can't comment on the capabilities of NTFS however.