Each of the three shooters has individually controllable aim and power, which is what makes the machine's nigh-miraculous accuracy possible.
Via TechnicBricks, here's how it works.
The shooter is meant to work as a Great Ball Contraption module (previously), accepting balls from an input, doing its thing with them, and then delivering them to an output. Only the (surprisingly large percentage of) balls that go through the basket go to the output.
Here's a Contraption composed of 17 of Akiyuky's modules.