From Rags to Richmond
The spectrum for the D-Class ranged from sub-level 1 to 7, increasing in proficiency.
The next level was the C-Class, which is the level Warren was currently at. He could control his own Reiteki, although his range was limited. He was only at sub-level 4. He could see that he needed to make a breakthrough if he ever wanted to reach the B-Class. However, he couldn't get any information for the Class that was above the B-Class.
'It must mean that I still need to cultivate my current level more efficiently so that I can get access to the higher level as well as gain new knowledge from the scripture that I received from the old man,' Warren thought.