What does Teabing point out about the painting of The Last Supper and what questions does it raise?

Teabing referred to a painting of The Last Supper to prove his point about Da Vinci hiding things in his work. He points out that there is no 'one cup', or Holy Grail, on the table, but all 13 disciples have their own cups. However, the painting shows the Holy Grail as a person, not a cup. Sophie is astonished that the Grail is a person and Langdon tells her that the person is a woman. The ancient symbol for a woman looks like a wide 'V' and is called a chalice. So, the Holy Grail represents a woman, a goddess. This makes Sophie question everything she has ever known about the Holy Grail and what they are actually looking for. Who the goddess is and how she ties in to Sophie and Langdon's quest remains to be seen.