But there is one more critical issue that complicates this reference. In Against Apion it mentions a period of 54 years and also 50 years, and a kingship in the 14th year!
Against Apion 21 21. These accounts agree with the true histories in our books; for in them it is written that Nebuchadnezzar, in the eighteenth year of his reign, laid our temple desolate, and so it lay in that state of obscurity for fifty years; but that in the second year of the reign of Cyrus its foundations were laid, and it was finished again in the second year of Darius. I will now add the records of the Phoenicians; for it will not be superfluous to give the reader demonstrations more than enough on this occasion. In them we have this enumeration of the times of their several kings: "Nabuchodonosor besieged Tyre for thirteen years in the days of Ithobal, their king; after him reigned Baal, ten years; after him were judges appointed, who judged the people: Ecnibalus, the son of Baslacus, two months; Chelbes, the son of Abdeus, ten months; Abbar, the high priest, three months; Mitgonus and Gerastratus, the sons of Abdelemus, were judges six years; after whom Balatorus reigned one year; after his death they sent and fetched Merbalus from Babylon, who reigned four years; after his death they sent for his brother Hirom, who reigned twenty years. Under his reign Cyrus became king of Persia." So that the whole interval is fifty-four years besides three months; for in the seventh year of the reign of Nebuchadnezzar he began to besiege Tyre, and Cyrus the Persian took the kingdom in the fourteenth year of Hirom.
Now besides the spurious 7-year reference for the siege of Tyre, the numbers given don't add up to 54 years. That is, from the 7th of Nebuchadnezzar to the 1st of Cyrus is not 54 years. With so many apparent contradictions, one option is to step back and look at this as a cryptic reference to some other event. Thus the 54 years and 50 years are relevant to the period from the fall of Jerusalem year 19 to the 1st of Cyrus as king over Persia, or the time of desolation from year 23, the year of the last deportation of many nations out of the land including the Jews to serve 70 years. In this context, to cut to the chase, if you count 13 years from year 7 of Nabonidus, then you arrive at the date for the fall of Babylon, not the fall of Tyre, suggesting Josephus is here using Tyre to cryptically give us the timeline for the fall of Babylon during the 20-year rule of Cyrus.
See continuation 1A