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. Click on the Image tab, then open the Image Size window and it will tell you the full pixels and file 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.
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.