I was dragging images into GIMP and noticed that GIMP indicated an image file size that was orders of magnitude higher than the original imported image. See pictures for context.

I was dragging images into GIMP and noticed that GIMP indicated an image file size that was orders of magnitude higher than the original imported image. See pictures for context.
This is normal.
images in files are usually compressed, and PNG compresses screenshots very efficiently. Gimp shows you how much memory it needs to have the image uncompressed in memory, typically,
And this for 8-bit mode, multiply by four in high-precision mode.
Image > Properties
gives you a bit more detail on memory usage.