To address your question "
I would like that someone could explain me the reason why the airflow entering the engine is lower when engine anti-ice is switch ON"
The air flow in the combustor section of the engine is lower because the Anti-Ice system has blead some of your compressor air, then dumping it overboard without returning it to the engine. Thus there is less air available for the combustor section.
As for the PW data quote, I got lost somewhere in the first sentence.............
Regards,
Old Smokey