Thanks for your report.
The layout of the dialog seems to be broken somehow.
There must be something specific about your machine/system.
Don't you have multiple displays? Did you try rebooting the machine?

Version of WinSCP: latest (5.15.2)

If the problem started to occur after upgrade... : n/a

Version of Microsoft Windows you are running WinSCP on: Windows 10 Home :(

Transfer protocol (SFTP, FTP, SCP, WebDAV or S3): SFTP

Mention if you use GUI or scripting/automation: GUI, Commander

If you experience an error, include full error message: n/a

Other data I consider sensitive: I have Blue markups on the screen capture graphic where (hopefully) irrelevant data is redacted.

Try to describe precise steps that lead to the problem - (I'm guessing this level of clarity isn't necessary, but I always try to follow the rules!):

1. Commander mode, select all local files in directory that I have just copied from remote directory
   
2. Right click list of local files and select properties.
   
3. Move resulting properties window to area below list of local files (in attached graphic, note markups I made, green arrow and box for correct file sizes)
   
4. Select all remote files in remote directory
   
5. Right click on remote files and select "Properties".
   
6. Alt+Tab to return local files properties window to foreground and compare to remote.
   
7. Note remote files properties number is not completely displayed (note markups I made, red arrow and box in attached graphic)
   

Let me know if I can help in any other way!
Roger

P.S. Awesome product!!! Thanks!