The market has gone through two rounds of declines. If investors did not seize the opportunity during the first wave of decline, then after entering during the second decline, they can simply judge the approximate first take-profit point of the second wave based on the space of the first wave of decline.
That is to say, the space of the second wave of decline is basically equal to the space of the first wave of decline, but it is important to note that this is not absolute; it is just how the market often behaves.
Why is this called the first take-profit point? Because the AB=CD exit method belongs to the active closing method, and the principle of the active closing method is that if the profit meets our expectations, we actively take profits. However, the declining market has not deteriorated, so AB=CD is generally used as the first take-profit point, but it may not necessarily be the final take-profit point.