As a divinatory line, nine at the second place of Decrease reads within the hexagram's overall concern with sincerity in one who practices decrease brings great good fortune, freedom from error, firmness and correctness maintained, advantage in every movement, and even in the use of two small dishes for sacrifice. The line occupies a place that does not match its own nature in the classical doctrine that odd places favour a firm, yang line and even places favour a yielding, yin line. It is also one of the two central lines of the hexagram, the place classical reading treats as the most balanced regardless of the line's own character. Its own text, that advantage in firm correctness, going forward would be evil, yet without decreasing himself he can still bring increase to others, is the particular fortune assigned to this one stage of the situation, not to the hexagram as a whole.
The second line corresponds by classical convention with the fifth line, and the two correspond here, since one line is yin and the other yang. Read together with the trigram it belongs to, Dui in the lower position of the figure, the line marks the situation settling into its own character, still wholly inside the lower trigram, one stage in the six stage movement the hexagram traces from its first line to its last.
A change at this line, from yang to its opposite, is the mechanism the tradition uses to move from one hexagram to another. Flipping the second line of Decrease turns Dui into Zhen while the other trigram, Gen, stays as it is, which yields Decrease's changing partner, Nourishment (King Wen 27), the hexagram this line is recorded as transforming into.