Thank you everyone for all your answers. I know it can be tough to understand what a person asks and colocation of people of course is much more superior when such subject is discussed. At lest we tried.
Let me explain why these questions are important to understand the system quicker and beyond the doubt.
Human language is very ambiguous. It differs from programming languages where in majority cases the result is predetermined. I am very accurate saying "majority" vs "all" since sometimes the result is not defined in programming languages too.
I asked the questions that allow one to narrow possibilities, a range of actions which a student can try.
For example my question, is the perception between these lines? Well, if yes, then I am not going to try and find something beyond these range and it will save a lot of time. Can you describe what you feel by saying perception to clarify? Why when you move too much, one line goes out and you do not see it anymore I can imagine lines everywhere? What does it mean?
Or what the center means... It is not that simple. When you look at a line behind the ball and the end of the line, the center is the same, any point at the vertical line that divides the ball in hals and continues to the line connecting the balls. If it is not the case when you are not looking behind that line. In this case the line connecting the cue ball and the object ball is not vertical anymore, it is diagonal.
Therefore, there are several possibilities that a person can think what the center of the ball is. See my diagram below. What is the center, #1,#2,#3, #4, or something else? I understand the diagram is not perfect and I see a little offset from the center, but I hope you get the point. I am not good at drawing.
Almost all my questions are like that. The goal is to remove ambiguity. If people were able to understand and explain these details, the learning process itself would be much easier and maybe one would not need to spend months before understanding the system. I believe the reason why it takes so long is because an ambiguity of the method communication to students. I am not taking into account psychological and physiological factors here that reside on top of it.