This site carries two Alexandrian lines and they are one line until 451. Dioscorus was deposed at Chalcedon; the imperial church installed Proterius in his place, and the Egyptian majority went on counting from Dioscorus. From that point there is a Coptic patriarch and a Greek one, both legitimately numbered, both in the same city, and neither list is a continuation of the other after the split — which is why the ordinals diverge and why a reader comparing them will find two men called the twenty-sixth. The History of the Patriarchs tells it from the Coptic side and is the only continuous narrative of that line; the Greek line is better documented in the imperial sources and worse documented in Egypt, which is the shape the evidence takes rather than a judgement about who was right. This project keeps both and marks the fork, in the same way it keeps both readings of Ignatius and both counts of the Seventy.
History of the Patriarchs of the Coptic Church of Alexandria · Life of the 25th patriarch (Dioscorus) and following