Photos that are scanned at 600dpi (dots per inch) stay the same size for viewing. Unlike photos, slides are scanned at 4,500 ppi (pixels per inch) because the 1.38” (35mm) wide slide is stretched over 100-inch screens to view. This stretching would leave the screen pixilated, unless we have enough pixels to fill the full screen.
Foto2Digital gives you those 6,000 pixels (1.38-inch x4,500 pixel/inch=6,000 pixels) so you can see the image with the same clarity as your parents did when the slide was captured.