Albert Barnes Commentary 2 Chronicles 17:14

"And this was the numbering of them according to their fathers` houses: Of Judah, the captains of thousands: Adnah the captain, and with him mighty men of valor three hundred thousand;" — 2 Chronicles 17:14 (ASV)

The captains of thousands; Adnah the chief. This literally means, “princes of thousands, Adnah the prince.” The writer does not mean that Adnah (or Jehohanan, 2 Chronicles 17:15) was in any way superior to the other “princes,” but only that he was one of them.

Three hundred thousand. This number, and those that follow in 2 Chronicles 17:15–18, have been regarded as corrupt by most critics for good reason:

1. They imply a minimum population of 1,480 per square mile, which is more than three times greater than that of any country in the known world (circa 1880s).
2. They produce a total that is exactly double the next largest estimate of Judah’s military force, the 580,000 mentioned in 2 Chronicles 14:8.
3. They are presented as a statement not of the whole military force, but only of the force maintained at Jerusalem (2 Chronicles 17:13; compare to 2 Chronicles 17:19).

It is probable that the original numbers have been lost and that the loss was supplied by a scribe who took 2 Chronicles 14:8 as his basis.