It's meant to express non-verbal disbelief or cause one to question the words just said, often used with comedy or sarcasm. In this instance his words were very "truthful", but his intentional nonverbal briefly raised question on them. He also started shaking his head "yes" during the next part only to go "no" briefly after he mentions 4 years. :)

It's meant to express non-verbal disbelief or cause one to question the words just said, often used with comedy or sarcasm. In this instance his words were very "truthful", but his intentional nonverbal briefly raised question on them.

It's meant to express non-verbal disbelief or cause one to question the words just said, often used with comedy or sarcasm. In this instance his words were very truthful, but his intentional nonverbal briefly raised question on them.