The eighth year - Jeremiah calls it the seventh year Jeremiah 52:28, a statement which implies only a different manner of counting regnal years.
Related Commentaries of 2 Kings 24:12
2 Kings 24:12
12 And Jehoiachin the king of Judah went out to the king of Babylon, he, and his mother, and his servants, and his princes, and his officers:c and the king of Babylon took him in the eighth year of his reign.