Again, the position of the gun in your hand as it fires has a huge effect on shot placement. No secret there.
The interesting part is using this chart to understand not simply how you should do it, but diagnosing where your technique is going wrong.
For example, if you pull the trigger with the wrong part of your index finger, it may rotate the barrel alignment ever so slightly in the wrong direction.
Thus, if you consistently hit to to right of your aim, you may be squeezing a bit too far to the inside of your index finger.