Cloud replicator setup with CosmosDB CoreSQL

Setting up a trial instance of Cloud Replicator in a Cloud Sandbox, using an account set up by our Azure admin team

Core Account Name – I am using the given Resource Name value

Core Account Access Key – I am using the given Primary Key value

Database – I am using the given Database value

Partition Key Postfix – what are the options here? Should I have received this from my Azure admin team? This field doesn\’t appear to be optional?

thanks