[Gimp-developer] Size on disk vs size reported on status bar

I was curious about the disparity in reported size between the size on disk in a file manager, and the size reported by "%m". I'm guessing "%m" is the size in memory?

For example, I have a GIMP 2.9 XCF that is 4000 x 6000 pixels, 7 layers. It's the early stages of a drawing, with very little information on the various layers, just the main outlines, some guidelines and a merged layer in shades of gray.

The size of the XCF file on disk is 11.5 MiB as measured by the Dolphin file manager. When I open the XCF file in GIMP, the size shown in the status bar is 3.8 GB.

Why such a huge difference in reported size?
