Instance initialization block and subclasses

I'm getting confused about when the instance initialization block should run. According to Kathy Sierra's book:

Instance init blocks run every time a class instance is created

So, consider having two classes: a parent and a child, according to this question and java's documentation:

instantiating a subclass object creates only 1 object of the subclass type, but invokes the constructors of all of its superclasses.

According to the above: why does the instance initialization block located in superclasses gets called every time an object of the subclass is instantiated? it isn't like that a new object of the superclass is instantiated.

After compilation instance init blocks become part of constructors. javac simply adds the init block to each constructor, that is this:

public class Test1 {
    int x;
    int y;

    {
        x = 1;
    }

    Test1() {
        y = 1;
    }
}

Is equivalent to this:

public class Test1 {
    int x;
    int y;

    Test1() {
        x = 1;
        y = 1;
    }
}

So the init block runs when constructor runs.