John Gill Commentary 2 Chronicles 17:16

"and next to him Amasiah the son of Zichri, who willingly offered himself unto Jehovah; and with him two hundred thousand mighty men of valor." — 2 Chronicles 17:16 (ASV)

And next him was Amasiah the son of Zichri
He encamped next to him, as the Targum:

who willingly offered himself unto the Lord ;
to fight the Lord's battles, and without any stipend, as some think; or, as Kimchi, he offered gold and silver to the treasures of the house of the Lord:

and with him two hundred thousand mighty men of valour ;
the number was 80,000 less than the former; the whole of Judah amounted to 780,000 men.