Boyd:  I said _ 50 _ .
Stiles: Really , I - I remember 20 . I do n't know . I have a really good verbal memory . And I remember 20 . I remember that distinct " twa " sound , " twa - enty . "
Boyd: I said fifty . With the " fa " sound . Hear the difference ?
Stiles: Uh ...
Boyd: If you ca n't , I can demonstrate some other words with the " fa " sound .