Need clearing up on Vision Paper

[kinganu123]

I was reading the Vision paper for java and three particular lines stuck out that i didn't entirely understand how to do.
1. "The exposure on the camera was set by intentionally overexposing the
image by shining a flashlight into the camera, allowing the auto exposure to reduce the sensitivity, then locking in that setting."
How would we "lock" the sensitivity. From what I understand, we'd have to stand in front of the robot with a flashlight every time it turns on to set overexpose it to light... Is that really what must be done?
2. It says that "a width and height of 30-400 and 40-400 pixels" is the criteria. Doesn't that change with the distance to the hoops? If so, how would I compensate for the pixel change? Or is that just a range of possible values?
3. What does "center of mass x value" mean? Is that the pixel location (which doesn't make sense because it would be coordinate points) for the center of a rectangle? I'm basically asking what this line of code means:

System.out.println("Particle: " + i + ":  Center of mass x: " + r.center_mass_x)