皮老師，8老師 a questions about 21 years old daughter

Dear 皮老師，8老師:

       thanks for your help before. i have a question as to

how to calculte the extended days dealing with  the eligibility to

apply Green card as dependent after 21 years old.

http://www.immihelp.com/immigrant-visa/cspa-calculator/

in the above table, we use birth day,   PD,   aproval day and

the visa bulletin currrent day.

on the I140, there are 3 dates: Priorite Date,  receipt date, notice date. 

according to my understanding, the extended days after 21 years old is actuuly:

notice date -  PD, is that right? 

the above table in the line seems everything is clear, then is it trustable?

if use  notice date - receipt date, then it make big difference. i think this is wrong.  

I am worrying, waiting for your answer. many thanks.