They are called Permanent Judges because they are required to sit on every appeal committee and court case relating to the Court of Final Appeal, and to distinguish them from other part-time jurists who also sit on the top court, known as Non-Permanent Judges.
At the founding of the court on 1 July 1997, as the Permanent Judges were all sworn in on the same day, they were sorted by seniority (whichever year they took Silk).
The Chief Justice sat in the middle; Henry Litton, being the most senior judge and would sit on the Chief Justice's right, with Charles Ching being the second most senior judge (sitting on the Chief Justice's left) and Kemal Bokhary being the least senior Permanent Judge, sitting on the right of Henry Litton.
[1] According to the Hong Kong Court of Final Appeal Ordinance, Permanent Judges are recommended by the Judicial Officers Recommendation Commission, and officially appointed by the Chief Executive.
(exact birth date not known) Note: Judges may have more than one graduate degree, and hence may be counted twice on this list