In tennis, the goal of the game is to hit the tennis ball over the net and within the lines on the other side of the court. Most of the time, it is obvious to both players whether the ball is “in” or “out”. The goal is to hit the ball to where to opposing player cannot return it, which is often the edges of the court, meaning that the ball frequently lands on or near the line. The official rule in tennis is that the returner gets to call if the ball is in or out.
One time when playing tennis I hit a very nice serve which lands just on the line, bouncing out of the reach of my opponent. Just as I clench my fist in joyful victory, he calls “out!” Knowing the rules, but also knowing the exact position of the ball, I walk closer to the net and ask if the ball really was out. He confirms that it was, and I pressure him to point to the spot where the ball landed. He of course points to the spot just outside the line, and continues to declare that my serve was indeed out. I say, “Alright, I’ll give it to you, but just so you know that serve was in.” He didn’t appreciate my comment very much.
In summary, the ball landed in a specific position, which was unaffected by the call of my opponent. Whether he saw it as in or out doesn’t affect the position of the ball, which, of course, was in.