C. F. Keil and Franz Delitzsch on 2 Chronicles 8:9-10

2Ch 8:9-10 שׁלישׁיו ושׁרי should be altered into ושׁלישׁיו שׂריו as in 1Ki 9:22, for שׁלישׁים are not chariot combatants, but royal adjutants; see on Exo 14:7 and 2Sa 23:8. Over the statute labourers 250 upper overseers were placed. נציבים שׂרי, chief of the superiors, i.e., chief overseer. The Keth. נציבים, praefecti, is the true reading; cf. 1Ch 18:13; 2Ch 17:2. The Keri has arisen out of 1Ki 9:23. These overseers were Israelites, while in the number 550 (1Ki 9:23) the Israelite and Canaanite upper overseers are both included; see on 2Ch 2:17. בּעם refers to כּל־העם, 2Ch 8:7, and denotes the Canaanite people who remained.