How and why can a Semaphore give out more permits than it was initialized with?

Question

I am reading the book Java Concurrency in Practice. In a section about java.util.concurrent.Semaphore, the below lines are present in the book. It is a comment abou

Answer 1

It is surprising to some of us.

You can easily subclass up a bounded semaphore.

/**
 * Terrible performance bounded semaphore.
 **/
 public class BoundedSemaphore extends Semaphore {
    private static final long serialVersionUID = -570124236163243243L;
    final int bound;
    public BoundedSemaphore(int permits) {
        super(permits);
        bound=permits;
    }

    @Override
    synchronized public void acquire() throws InterruptedException {
        super.acquire();
    }

    @Override
    synchronized public boolean tryAcquire() {
        return super.tryAcquire();
    }

    @Override
    synchronized public void release() {
        if( availablePermits()