I am personally of the mind that free, advanced, and casual, are defined not by the length of their products, but by the quality of their work; common sentiment. I would recommend you don't size yourself and your skills up merely by how long you can write, but how intricate it is, and how well it flows. Cleverness in linguistics and avoiding the common mishaps in writing are what really defines a person to me, and really should be how it is for everyone frankly. 

Explaining things quickly, and concisely, much like in science, is equally so in writing, a hallmark of skill in my eyes. There're times where one should pay close attention to detail, and other times where one ought to focus on the more esoteric. Ultimately, it is all about how synergetic you are with the story itself.

I feel like a lot of writers need to hear a lot that the hallmarks of writing aren't about how much you can churn out, but rather how well you churn it out.

So at risk of avoiding your question, but really just because I think confining oneself to simple classification is just a wrong perspective, you ought to identify yourself as you see fit. "I'm a writer with adequate experience and an interest in the hobby," is an equally acceptable description as "I'm low-casual" or whatever else.