Kanban size calculation

Hi everybody,

I want to use the Kanban formula to calculate automatically the kanban size for Production and Supplier source. what i did until now was to

Create Bill of Material
Define Pull Sequence
Enter a Forecast/MDS/MPS
Define Kanban Plan
Launch Kanban Plan
Generate Kanban Cards
Print Cards
Initiate Replenishment Process

can you tell me what I've missed or if I did something wrong, because the kanban size is not updated automatically

Also I found a note where it seems that you can calculate this size only for new cards...is this true, or i can calculate also for existing cards