How calculate a delta between 2 periods ?

[#1]

Dear all,

I would like calculate a delta between 2 different periods.

For example, I have a list of pieces that are missing.

I've got the number of missing by references about 2 week different via a pivot table in Qliksense.

I would like to create another one that allows me to see the increase or decrease by missing references.

I think it's the sum of missing in week x -  sum missing in week y.

How translate this term in QlikSense ?

I would like to have a delta of this table.

Thanks for your help.

Corentin BOUR