monthly backup - different folder size

Hi all,

i just started to make my monthly full backup. After copying, one folder has different file count, and different size on source and copy.

Difference is one file, having approximately 17 mb. See picture.

What is "best to do" to identify and find the missing file?

Is there something that can do a "find a file with the size of xyz in folder abc"?

And funnily, source and copy show same creation date and same change date. Is this a bug or is this a feature?

Machine is Mac Pro mid 2012, os is 10.13.6

Thanks in advance!

Greetings fro germany

Chris