Analysis for Out of stock Kanban cards

Hello,

I have created a kanban for material replenishment.
As you can see there are 2 kanban cards for each part number, one with a trigger of half total stock, and another one for if stock reaches zero.

A helpful KPI is to know the number of parts that are out of stock. However, if I set a simple analysis that works out Qty of cards where Empty=Yes and trigger =0, if the first card (trigger at half total stock) is replenished, it will be showing as Out of stock.

Any ideas for this?

I guess what I am after is a way of telling how many different parts have BOTH Kanban’s empty.