Yes—an extreme diopter setting does not automatically mean your vision is very poor. A few things can explain it:

• You may be interpreting the scale direction backwards; what looks like the “lowest” end may actually correspond to the more positive setting.
• Even with good distance vision, some people need positive correction for very close viewing, similar to needing reading glasses.
• You may also have a small amount of myopia or another minor vision difference without realizing it.
• The camera’s diopter calibration is not perfect for every user, and small differences in how close you hold the camera to your eye can affect what looks sharp.

The best way to set the diopter is to adjust it while looking at the viewfinder’s etched AF points or display markings, not the scene itself. If those markings look crisp, the diopter is set correctly for your eye. If you’re unsure about your eyesight, only an actual eye test can confirm it.