The area I fly from is 8.1 miles from the Phila International Airport. I measured from the end of the closest runway to my take off point. I do not understand why I constantly get "Caution, Class B" warnings. I am way past the 5 miles I need to be from the airport. All the planes which fly over me are at from 1,900 to 2,400 feet in altitude. (Data from AltitudeAngel.com) Why am I receiving these warnings ?