2 Chronicles 2:2

2 And Solomon told out threescore and ten thousand men to bear burdens, and fourscore thousand to hew in the mountain, and three thousand and six hundred to oversee them.

1 Kings 5:15-16

15 And Solomon had threescore and ten thousand that bare burdens, and fourscore thousand hewers in the mountains;
16 Beside the chief of Solomon's officers which were over the work, three thousand and three hundred, which ruled over the people that wrought in the work.

Were there 3,600 or 3,300 overseers?

Read carefully. The 3,300 is "beside the chief of Solomon's officers which were over the work".

That means that there were 300 such chief officers that ruled over the 3,300 regular officers, who in turn ruled over the 70,000 workers.

Alternatively, we can recognize that if Solomon had 3,600 chief officers, it is also true that he had 3,300 chief officers. In that case, the writer of First Kings was being less precise than the author of Second Chronicles.