Can't get a roll up to work within the same table


I have a very simple table set up for Book in & book out materials

View 1: is for my book in of materials
View 2 : is for booking out materials

In view 2 I’ve put a linking field restricted to only search in view 1 aswell as a number field (for book out quantity).
In View 1I’ve created a roll up field that sums up the total use of a particular material from my View 2 - however the roll up field just gives me a 0.
What am I doing wrong - or is it me who has misunderstood the roll up capabilities in the same table?

I know similar can be done across different tables - Im just trying to keep it visually simple.