This episode covers chapters 3-5 of the manga.
While Ryuk looks at Light, he sees the numbers 9, 3, 31, 26, 3, 9. These numbers are the lifespan of Light and only Shinigami can interpret these numbers.
If you look closely at one of Light's papers, you can see his birthday at the top, February 22, 1986.
L: This is still a theory. Also, based on the fact that he's killing criminals...this person is acting under a strong sense of justice. It may be...that he's trying to become God. We must say this is a very childish mentality.
Ryuk: The price of a Death God's eyes is... half of that human's remaining lifespan.