Fix image size parsing for xz method

[HovnovoD]

Hi,

I found an issue in the script related to the xz method. The output contained special characters, which caused the image size to display incorrectly. As a result, the RESTORE function would exit without writing to disk.

I modified the script so that only numeric characters are kept when parsing the size. This ensures both the RESTORE function and the image size display function work correctly.

I apologize for the confusion and for reopening the Pull Request, as I am still a beginner.

Thanks for the great script.

Regards HovnovoD