What is the difference between camera magnification and actual (screen) magnification?

Camera magnification is the magnification of the camera itself. The Fluke Networks FT600 FiberInspector Pro has a dual magnification camera that has a magnification of either 250X or 400X.
When it comes to display magnification it gets tricky. The display magnification is a direct relationship between the magnification and the screen size. A smaller screen will yield a smaller display magnification; whereas a larger screen will show a larger magnification.
One method to determine the screen magnification is to take a rule, measure the diameter of the cladding (including the core) in millimeters (mm). Then take this number and divide it by 0.128 it will give you an approximate magnification of the fiber end face on the instruments display.
For Example: 
The diameter of this fiber end face image is approximately 25 mm. If we divided 25 mm by 0.128, the approximate display magnification of this image would be 195.31X