Sure. When you count 6 and 4 left on base, you are adding up the number of runners who were on base when the inning ended.
That's a kind of team stat. But the box score records a stat on a per player basis. Take for instance a lead-off single followed by three strikeouts. Each of batters 2 through 4 left a runner on base. So at the end of the inning, 1 runner is left on base, but the box will show 3 failures to score the runner.