Options/Show all file sizes in:

Explorer++

Tools/Options.../Show all file sizes in:

System Default:   Flexible, Bytes if option enabled
 

When this box is cleared, drive and file sizes (and folder sizes, if enabled) are displayed in a flexible format, that is, in bytes, kilobytes (KB - 103 bytes), megabytes (MB - 106 bytes), etc., depending on file size.

Checking the box allows the user to choose from a variety of units, from bytes up to terabytes (1012 bytes) and even petabytes (1015 bytes)!  File sizes will be displayed in the chosen units, even if files are small.  This might prove useful in viewing the sizes of larger drives, etc. or media files (DVD files could be in the gigabyte (109 bytes) range