How is the Waiting List Dynamics calculated?

Waiting List Dynamics updates on a weekly basis.

When ALL is selected – the number of additions is the sum of the number of referrals captured for the first time on the waiting list that week (regardless of category).
When a category is selected, the number is represents the sum of the number of referrals became a 1 or 2 or 3 that week.
Referrals that have been re-categorised will appear as additions on each list they have been categorised.
The number represented in ALL is not equal to sum of 1, 2 , 3.
The purpose of the calculation this way is to collect changing demand NOT waiting list movements.