aws:userid for the IAM principal used by a Gitlab runner

Hello!

I am trying to set up multi-account AWS SAM deployments with GitLab CI/CD by following this article[How to set up multi-account AWS SAM deployments with GitLab CI/CD]

While setting up, in step 2, it asked for The aws:userid for the IAM principal used by the Gitlab runner.

I have gitlab runner on AWS EC2 instance and it doesn’t have any IAM role attached to it. And, the runner is working perfectly fine.

Problem is, I can’t get the idea of this aws:userid that I need to paste to follow the article.
What exactly i need to input here as the value of “CIAccountSTSCondition”?