If you have installed the supplementary function Tool Management, you will see the T button on operation rows. In the window that opens when you click the T button, you can change, add or delete tools that are linked to an operation. If a tool "contains several entities", you cannot change the quantity but you can choose an entity.
If a quantity has been reported for this operation, you cannot change anything on the already linked tools (the tools are greyed out).
Read more about this under Tool Management in Adding / Replanning.