Restricting the multiplicity of an association is not permitted when trying to add access context

I am trying to restrict the data of our custom OWL so that employees only see data that is relevant to them based on our territory structure.

I tried following the instructions here:

Define Access Control

How to set up access control/ define access context

The association was already set up, so I thought I would simpy add the keyword to the beginning.

This association is part of my root node.

However when I try to activate, cloud studio tells me to stop trying to change the multiplicity?

See below:

I tried the same for territory but get the same error.

Can someone tell me why it is changing the multiplicity?

Would this have anything to do with the way I have structured my SADL query in my OWL?

The OWL displays the child node in the Result List and links ToParent to display the rest of the data.

If this is causing the issue, how can I restrict on customer/territory while still displaying the child node in the result list?