Do they mean 4th century B.C. or 4th century A.D.?
Not sure, although I’m inclined to think AD, Roman era, even though it was over 1000 years old by 400 AD.
https://en.wikipedia.org/wiki/Ordu#History
https://en.wikipedia.org/wiki/Ordu#Archaeology
Periplus of the Euxine Sea by Arrian of Nicomedia (ref to its ancient name, Cotyora)
https://topostext.org/work/203
ยง 23 From the Thermodon to the river Beris ninety stadia. From the Beris to the river Thoaris sixty stadia. From Thoaris to Oenoe thirty stadia. From Oenoe to the river Phigamus forty stadia. From Phigamus to the fortress of Phadisana one hundred and fifty stadia. From Phadisana to the city of Polemonium ten stadia. From Polemonium to the promontory called the Jasonian an hundred and thirty stadia. From the Jasonian promontory to the island of the Cilices fifteen stadia. From this island to Boona, where there is a port for ships, seventy-five stadia. From Boona to Cotyora ninety stadia. Xenophon mentions Cotyora as a city, and says, that it was a colony of the Sinopians: at present it is no more than a village, and that not a large one. From Cotyora to the river Melanthius is, at the utmost, sixty stadia.