You can't see any wheels in the car. It is impossible to judge the wheel position without repeated mechanical exercises such as turning, turning and turning. This kind of judgment is difficult to express in words, and we can only rely on our countless practice to raise ourselves from perceptual knowledge to rational knowledge.
You aim at the position of the stone and then dozens of centimeters to the right is the position of 30cm. If the right front wheel is right in the middle of the stone, it is 30cm plus half the tire width.
A little experience, learn from you.