The random numbers you see are actually the sector numbers. During deep scan or scan using the “physical disk” option, the software will scan your device using the raw recovery technique (sector by sector search). A combination of alphanumeric characters is displayed instead of the original file names.
In case of images, during preview you can see the image resolution and other details if they are available. However, in case if other file formats you will only be able to see the sector numbers.