Why are the trains from Beijing to Dalian and Dalian to Beijing all odd? Isn't the uplink even and the downlink odd?

Shenyang is high, Beijing and Dalian are low. After Shenyang, the trains will become even and odd numbers.

Direction from Beijing to Dalian: K68 1 from Beijing to Shenyang and K684； from Shenyang to Dalian;

Direction from Dalian to Beijing: Dalian to Shenyang is K683 and Shenyang to Beijing is K682.

So many trains you find on the train timetable are even or even 3, which changes in real time according to the actual running direction and direction of the train. Long-distance buses usually have to change trains when passing through Beijing.