Thank you for so many good suggestions and related resources.
If I have found those resources, I would not have created the above applet.
I created that one, because someone saw my vernier applet and want to find applet for micrometer.
Because I did not found similar applets so I created this one with EJS.
I should not have display the values for x2,x3. There are not related to the reading. It is used for change the distance (and those value are for internal program used).

Anyway, I have already modified the code according to your suggestions. I hope you will like the new design.
Suggestions are welcomed!