John Gill Commentary 2 Kings 8:17

"Thirty and two years old was he when he began to reign; and he reigned eight years in Jerusalem." — 2 Kings 8:17 (ASV)

Thirty and two years old was he when he began to reign
The second time, in the lifetime of his father:

and he reigned eight years in Jerusalem ;
which ended in the twelfth year of Joram king of Israel, (2 Kings 8:25) .