Jamieson, Fausset and Brown on 1 Chronicles 11:11-13

11-13. Jashobeam, an Hachmonite--or, "son of Hachmoni." He is called also son of Zabdiel (1Ch 27:2), so that, strictly speaking, he was the grandson of Hachmoni (compare 1Ch 27:32).

lifted up his spear against three hundred slain by him at one time--The feat is said (2Sa 23:8) to have been a slaughter of eight hundred in one day. Some endeavor to reconcile the statements in that passage and in this by supposing that he slew eight hundred on one occasion and three hundred on another; while others conjecture that he attacked a body of eight hundred, and, having slain three hundred of them, the rest fled [Lightfoot].