Weird Normalized issue

I started off with -4.5 in my left eye and -3.5 in my right eye.

Using my eyechart, I reduced my left to -3.5 and my right to -2.75 because I was able to read 20.30 with those lenses.

On a bright sunny day, with natural lighting, my right eye can now read 20/15. My left is still stuck at 20/30. Why does this happen? Any thoughts?

It’s only been about a month of using normalized lenses, btw.

You started off with OD/OS -3.50/-4.50. The difference between both eyes is 1 diopter.
You reduced to OD/OS -2.75/-3.50. The difference between both eyes is now 0.75 diopters.

If you had reduced to OD/OS -2.75/-3.75, you’d probably be saying you can read 20/15 in both eyes, because there’s still a gap of 1. Because your left eye is now 0.25 weaker than your right eye compared to how it used to be, you probably should stay on that reduction and wait for your left eye to catch up with your right eye, and for the difference in diopters between both eyes to become 0.75. At the moment the difference is closer to 1, because that’s what your eyes are used to.

So you would stick with the -2.75 and -3.5, rather than bring the right down to -2.5?

No, do what you’re doing now and wait for it to equalise.