On certain occasions, the calculation of completeness (the installation progress) shows negative numbers, such as "-80%" and that sometimes starts way above "-100%", such as "-130%" and then it is slowly decreasing to "0%" as the installation nears its completeness.

Version:
anaconda-webui-39.29-1.fc39.x86_64



Reproducible: Always

Steps to Reproduce:
This was quite difficult to reproduce, but I finally managed.

1. Use the current Fedora installer (no webui) and generate the default layout (btrfs with /root and /home). Alternatively, you can use the webui with "Erase all" which produces the default layout, too.
2. Reboot the machine.
3. Boot into the Live system, install `anaconda-webui` and start it.
4. Select the option to reuse the mountpoints.
5. Assign both /boot and /root from the previous installation, using the btrfs root subvolume for /root.
6. Add another mountpoint, /boot, and assign the btrfs home subvolume from the previous installation.
7. Confirm and start the installation.
8. Watch the progress meter.
Actual Results:  
The progress meter shows negative numbers.

Expected Results:  
The progress meter should show positive numbers from 0 to 100, as the installation progresses.

See the attached images.