I am really sorry I decided to use the app for this post, I shall try and rectify the issue. (It was intended for general discussion.)
The unit measurement is diopter. As I am nearsighted the reading is -4 in both eyes.
How old are you? I'm very nearsighted myself. As I recall, my prescription gradually became stronger while I was still growing, then stabilized around age 20. This was many years ago, so I don't remember the exact timeline. But definitely consult your ophthalmologist to find out whether your situation is normal or whether something else is going on.