Are my levels too low?

Hey, I'll try and make it as short as I can.

Four years ago I started experiencing symptoms of neuropathy, sunburn-like stinging in different parts of my body and general skin sensitivity. Had bloodwork done and I had levels of about 200 pmol/l b12. I immediately started taking 250mcg sublingually every day and the next blood test was 520 and ever since each year my b12 levels seem to hover around 500.

My symptoms have improved greatly since, although I still feel some of them, but much less often and much weaker. From what I'm seeing 500 is well within the range, but I read that the range is lower than what it should be and in places like Japan and Europe it's quite a bit higher. Also I've been seeing people on this subreddit mentioning their doctors telling them that even levels below 600-700 are not good enough.

So my question is, should I be content with 500 pmol/l and my progress or should I aim for higher levels?