There's a stat in there called failure percentage, the number of times a batter fails to reach 20. Bell is top (or bottom) at 48.57. Pietersen's percentage is 41.18, which is good, presumably, given his record.
Bowlers like to think it's a batter's game. This stat says it's not - you fail almost half the times you try. And they wonder why batsmen become weird and neurotic.