Image File Size Is Too Large

This may be a repeat. Must have hit the wrong key while editing the original version and it disappeared. Anyway, I am using Acronis 2014 with a Windows 8.1 system. The C:\ drive size is 180 GB Used and 798 GB Free per Properties. When I make a normal image the image file size is shown by Acronis at 377 GB and by Windows Explorer properties as 409 GB Used and 70 GB free. When I do a Hifh compression backup, Acronis shows 5.12 GB while Windows Explorer/Properties shows 128 GB. Why is the image file so large when the actual disk data is much smaller? Why did compression increase image file size. I am mucho confused.

kwhiz01