It is assumed that the fluctuation range of the market is almost equal to that of the price. In this way, if the market rises by 30 points and then falls back, it means that it will rise by about 30 points from the lowest price of the callback.
Although the concept of measuring motion is too simple to seem credible. But the frequency of this method to provide reasonable instructions is beyond people's imagination.
Communicate with each other, hehe ...