What is difference between File size and Size in the output of GET-VHD command?

In resizing VHD using Resize-VHD command, the property SizeinBytes is accepting value greater than the "Size" property in the output of the GET-VHD command. But my actual size of VHD is in "FileSize"  property. I am unable to figure out the relation between File size and Size.

I would be glad to know the relation between the FileSize and Size properties or the unit of Size property (Kb/Mb/any other related). 

Output of Get-VHD command

 Thank you in advance