1. This is the tracking of your parcel:
Number: RK443942550CN
Package Status: In Transit

Destination Country: Korea, South
2016-10-20 17:04 CNSZHA, Departure from outward office of exchange, Dispatch number : 407
2016-10-19 11:13 21502700, Posting/Collection, Posting office zip code : 21502700, Transit or Destination country : KOREA

Origin Country: China
2016-10-23 03:57 Shanghai Pudong, left
2016-10-23 03:57 Shanghai Pudong, left hand navigation
2016-10-21 09:26 Shanghai Pudong, reach
2016-10-20 08:33 Suzhou Exchange Bureau, have been exported directly
2016-10-20 08:18 Suzhou Exchange Bureau, have been exported to open
2016-10-19 20:36 Bulk mail processing center, Suzhou city, away, the next stop "Center of Suzhou"
2016-10-19 15:07 Bulk mail processing center, Suzhou has been sent
2016-10-19 11:13 Bulk mail processing center, Suzhou has been accepted
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2. According to the above tracking, your parcel seem to be fine. I don't see any problem with it. The arrival time you are pointing is China Post Airmail Parcel Estimate Arrival Time. As you can see Estimate, this does not mean it is accurate all the time.

3. Your parcel is fine, you just need to be patient and continue to track your parcel on the South Korean Postal site.

Hope this help.