Notification based on seen status

I have requirement which is i want to show notification to set of users based on they seen it or not

for example i have a doctype book while creating book doctype i ticked track seen checkbox so i can track user’s who are seen it and not seen it

and i added notifications.py file in my customapps/customapps/notifications.py

and i added below code in

from future import unicode_literals

def get_notification_config():
return { “for_doctype”:
{
“Book”:{"_seen":(“in”,[‘Administrator’]) },
}
}

what i am getting on notification bar 3 instead of 7 because i have 7 books which are not seen and 3 which are seen

please help me