My file size is 92.3 mg while my file size in memory is 466.4 mg.
Whats the difference?

The image in memory will generally be larger because they have no compression. Some files use compression (lossy or lossless), so the physical files will still be smaller than what the image consumes in memory.

The memory size also includes UNDO memory.

My files are saved in .png...loseless. Although I do not remember if the "compression level" slider was high or low, if it makes a difference.

The file I referred to above did have a lot of work done to it, so maybe the "undo" memory accounts for it. However, I get the same numbers from a file that I have not edited yet.

Its not a real important question, I just wondered about it. I have a lot more troubling questions coming up :-)

The undo memory usage can get very large.