2 Samuel 23:8
8 These be the names of the mighty men whom David had: The Tachmonite that sat in the seat, chief among the captains; the same was Adino the Eznite: he lift up his spear against eight hundred, whom he slew at one time.
1 Chronicles 11:11
11 And this is the number of the mighty men whom David had; Jashobeam, an Hachmonite, the chief of the captains: he lifted up his spear against three hundred slain by him at one time.
The person who raised this contradiction (Dan Barker) was being dishonest, for a few reasons.
First, he didn't mention the chief captain's name, because then it would've been obvious that these are two different people. At the time of 2 Samuel, the chief captain is named Adino, and in Chronicles the chief captain is Jashobeam. They left that out of the video. Liars.
Secondly, these chapters are very obviously set at different time periods:
2 Samuel 23:1
1 Now these be the last words of David. David the son of Jesse said, and the man who was raised up on high, the anointed of the God of Jacob, and the sweet psalmist of Israel, said,
1 Chronicles 11:9
9 So David waxed greater and greater: for the Lord of hosts was with him
The chapter in 2 Samuel is set towards the end of David's life, whereas the chapter in 1 Chronicles is during the time when David is rising in power. Between those two points, David's chief captain changed. David reigned for forty years (2 Samuel 5:4), meaning this probably happened a half dozen times or more as the captains aged out.
The fact that someone would present this as a contradiction demonstrates that they are only pretending to care about the truth. They are being lazy, or if they know better, they are being extremely dishonest.