ما يعنيه ذلك هو أنك إن إلتقيت بشخص ما، وتم إخبارك، أوه يبلغ طول والده ستة أقدام، كم ستعرف حول طوله؟
What that means is if you met somebody,  and you were told, "Oh his father is six feet tall,"  how much would you know about his height?