In games this season where Charles had 20 or more carries, he has 159 rushes for 933 yards (5.9 yards per carry).
In games where he had less than 20 carries this season, he has 112 rushes for 523 yards (4.7 yards per carry).
Both are good numbers, but it seems like getting more carries helps him.
Interestingly, there were three games where he had fewer than 10 carries. If he'd been given the ball more and gained the average number of yards in his other 12 games, he'd be at 1,799 yards right now.
Chiefs Football - 2014 (and every other year)