Don't worry, friend. In order to see your image in its full glory, open the file in Photoshop or Lightroom—this will show you the true scan size.
- From the menu click on Image -> Image Size
- (Windows: “ALT+CTRL+I” Mac: “Option + Command + I”)
You will see the full resolution in pixels (px) and see the image size of your file (scan size) in MB.
Measuring files can be a bit complex. There are two different measurements for your files, and they are not the same thing: the "image size" and the "file size".
Image size refers to the pixel dimensions of the file multiplied by the number of bytes per pixel—this is the true size of your image that you will see when you open it in Photoshop or Lightroom. This is what we refer to when we talk about scan size and your image size.
File size refers to the size the digital file takes up on a disk—it sometimes appears smaller than the image size because your computer will abbreviate certain data in your file to take up less space. However, it does not effect the size/resolution of your image.
You can think of these different sizes like a math equation: 2+2+2+2+2+1 and (2x5)+1 both have the same value, even though one way of writing the equation is larger than the other.