What are "credentials" on "confluent_kafka_topic" resource?

What does the credentials block on the confluent_kafka_topic resource do?

I am familiar with credentials on the confluent_kafka_acl resource. The presence of credentials on this resource will add an ACL to the API key to access the specified resource.

But, I don’t understand how credentials on confluent_kafka_topic applies because I don’t see that an ACL can be applied directly to a topic.

Here is a screenshot of the plan that Terraform created for it. Our concern is that the credentials on the topic are changing - would that affect existing clients?