Your "Personal Number" is a combination of your "Drift" + the number of boards you miss your ankle by when you bowl, 7 as a common reference point. If you want to find the exact number, get someone to watch you from behind when you bowl and record which board your slide foot finishes on and which board the centre of the ball passed over.
DRIFT
So to begin with, we have to find how much you drift. Easiest way, line up on the approach with your slide foot covering the centre dot board (19).
Bowl your normal strike feeling towards the 2nd arrow (board 10), doesn't matter if it doesn't hit the mark just that you're aiming toward it with your strike bowl.
When you've achieved a good strike feeling, remain at the foul line without moving your sliding foot and look to see where it is in relation to the centre dot board 19. You will either be covering the centre dot with your slide foot or be to the left or right of it.
You determine your "drift" by counting how many boards to the left or right of the centre dot your slide foot finishes. Don't count the centre dot board, do include the board you finish on.
Repeat the process about 10-12 times, each time you achieve a good strike feeling make a note of the number of boards. The most common number (of boards) is your Drift. This process will show you if you drift Left or Right and the number of boards or no drift (straight ahead).
PERSONAL NUMBER (PN)
So, we start with 7 as the common starting number (this is the distance from centre of ball to inside ankle of slide foot), to this we either add or subtract the number of boards you Drift.
Right hand bowler who drifts to the right, add your drift to 7 = PN
Right hand bowler who drifts to the left, subtract your drift from 7 = PN
Left hand bowler who drifts to the left, add your drift to 7 = PN
Left hand bowler who drifts to the right, subtract your drift from 7 = PN
Left or Right hand bowlers with 0 drift, PN = 7
Just remember, Right hander to right and Left hander to left PN = 7 + drift
Right hander to left and Left hander to right PN = 7 - drift
EG. Right hander drifts to rights 5 boards. 7 + 5 PN = 12
Right hand drifts to right 4 boards. 7 + 4 PN = 11
Right hand drifts to right 3 boards. 7 + 3 PN = 10
Same for Left hander drifting to left.
Right hander drift to left 5 boards. 7 - 5 PN = 2
Right hander drift to left 4 boards. 7 - 4 PN = 3
Right hander drift to left 3 boards. 7 - 3 PN = 4
Same for Left hander drifting to the right.
What does all this mean??
It lets you know where to stand on the approach so you'll be able to put the ball over a specific board at the foul line on the way to your target. You'll be more likely to be able to repeat a shot knowing exactally where you started from.
Sorry to all for such a long post. All this does go to show that Storm Super School does teach you something. I hope this has helped someone
Cheers,
Gary