Why this backup file size is way larger?

I have lots of .CDR files whose backup files are mostly almost the same size of their original files.

But this one backup file in particular is way larger.

The .CDR file contents are merely a 488.0 x 544.0 mm page with a 420.0 x 480.0 mm rectangle with no fill.

Why is that? TIA.

Windows 10 Pro 22H2 19045.2364
Windows Feature Experience Pack 120.2212.4190.0