The I1 interceptor is called before the I2 interceptor because you have overwritten the order in beans.xml:

<interceptors>
	<class>tangyong.javaee.understadingcdi.basic14.I1</class>
	<class>tangyong.javaee.understadingcdi.basic14.I2</class>
</interceptors>

See Interceptors spec., section 2.1 Interceptor Definition:

A deployment descriptor may be used to specify the invocation order of interceptors or to override the order specified in metadata annotations.

Here are the two interceptor classes (so the others don't have to download the .zip)

@Priority(Interceptor.Priority.APPLICATION + 10)
public class I2 {...}

@Priority(Interceptor.Priority.APPLICATION + 20)
public class I1 {...}