If you have selected files in Copywhiz using File Explorer (Windows Explorer), then go to the destination folder. Right-click inside the folder, choose Copywhiz → Paste Advanced to open the Copywhiz window and click on the 'Advanced Settings' button as shown in the picture below.
If you have Copywhiz's main window already open, then you can directly click on the 'Advanced Settings' button as shown in the picture below.
Now select the 'Source' tab. The following window will appear.
Here, you can specify the file size criteria based on which the files must be copied.
Press the OK button and then click on the 'Paste Now' button to paste files based on the file size criteria. A sound plays, indicating successful completion of a file copy task.