OK. So bandwidth is something limited on the curve (you call it central line?). I tried a purple dot, dragged Q but it stopped on the number 2. Does any Q have his limits? I am not sure I saw something on the curve, do you see the change? Then I tried a green dot. You see what larger the number comes, in the beginning the colour on the line (Q?) goes wider but what larger number than more narrow the bandwidth on the curve comes, while finally only dot remains. And then I reduced Q (numbers) and on the line green colur appeared more, widely... Where is the sense of that? What larger number than wider Q has to be, right? If I choose (use) a Q, what I will notice - the number, or what happens on the curve? Does central line is the right word, or no matter which, in English?