Winclone rather slow, backup folder much too small

Hi everybody,
I am using Winclone 8.2 on MacOS Catalina 10.15.7 and today performed a backup of my Bootcamp partition which has 259 GB. The Winclone Backup lasted for 3 and a half hour and the resulting backup folder was only 139,6 MB! The program says successful backup, no error, and the verifying process went fine too. So I checked the log file. Here I found a lot of remarks like “Last message repeated 82 times” and sometimes even repeated 300 times. The log file says it completed 186 GB which could be a reasonable amount of data concerning the 259 GB bootcamp folder.
But now I am not sure, whether I could rely on this backup in times of “Russian Cyber attacks”. Could anybody help me??
Greetings from Germany!
Wolfgang Lueg

We did some time trials here:

As for the image size, look in the image by right clicking on it in the finder and selecting “show package contents” , then look at Windows.wim or boot.img.gz. Those are the actual data files and the size is more accurate.