What does 2 Chronicles 33:1 mean?

2 Chronicles 33:1 KJV
Manasseh [was] twelve years old when he began to reign, and he reigned fifty and five years in Jerusalem:

2 Chronicles 33:1 MKJV
Manasseh [was] twelve years old when he began to reign, and he reigned fifty-five years in Jerusalem.

2 Chronicles 33:1 NKJV
Manasseh [was] twelve years old when he became king, and he reigned fifty-five years in Jerusalem.

2 Chronicles 33:1 KJV 2000
Manasseh was twelve years old when he began to reign, and he reigned fifty and five years in Jerusalem:

Interlinear KJV

Manasseh /M@nashsheh/ was twelve /sh@nayim/ /`asar/ years /shaneh (in pl. only),/ old /ben/ when he began to reign, /malak/ and he reigned /malak/ fifty /chamishshiym/ and five /chamesh/ years /shaneh (in pl. only),/ in Jerusalem: /Y@ruwshalaim/

Annotated Bible

Manasseh’s long reign of fifty-five years is marked by flagrant sins and great misery. He pollutes the Temple with the worst forms of idolatry (1-10), until he is taken prisoner to Babylon, where he humbles himself, and is forgiven and restored (11-13). Then he repairs the city, removes the idols, and restores the worship of Jehovah (14-20). His wicked son Amon reigns only two years, being murdered by his own servants (21-25). The narrative is parallel with 2Ki 21:1-26 adding the account of Manasseh’s captivity, repentance, and restoration.

Patrick/Lowth/Whitby/Lowman Commentary

See 2Ki 21:1, where his mother’s name is set down, which is here omitted.

He repaired the altar of the Lord, and sacrificed thereon. For now he was sensible there was no other God but the Lord, who had wonderfully delivered him out of captivity, and restored him to his kingdom when he implored his mercy.

And command Judah to serve the Lord. This was a proof of his true repentance, that he endeavoured to bring his people back to the service of God, whom he had misled (verse 9) to the worship of idols. But, as Kimchi notes, he was not able to do so much good as he had done mischief, for the people continued their inclination to idolatry; and neglected the study of the law of God. For in Josiah’s reign (which presently followed) it was a matter of great surprise that they found the book of the law, when they were repairing the temple: the copies of it, as the Jews think, having been destroyed in the time of Manasseh and Amon. But it is not credible, which were preserved in the hands of the ten tribes, and without which the church could not have been reformed.