My screen is 1280 x 800 pixels. The screen has a horizontal dimension of about 12 inches. That gives about 106 pixels per inch. There are larger screens with the same resoltuion that would have closer to the average 96 pixels/inch that you mention. Most PC's can be set up with different screen resolutions depending on how the user prefers to see text and graphics displayed. Mine can be set as low as 800 x 600 pixels which would make objects almost 50% larger.

The point is that you can't tell for sure how large a scan is going to appear to a viewer unless you know the dimensions and resolution of his PC screen. Every pixel you send to the screen will be displayed somewhere; with lower resolution screens the pixels will be spaced physically further apart and the object you scanned will appear larger.