When using Network Load Balancer what function is Client source IP among Session affinity fun

[SeongGi]

When using Network Load Balancer (TCP/SSL) with GCP If you look at Session affinity, there is a Client Source IP. At first, I thought the function was to remove the XFF header and see the original USER IP

Looking at the explanation, I don't think it's right. I want to understand that, but it doesn't exist in Google Docs. I want to know about that part.

https://developer.mozilla.org/ko/docs/Web/HTTP/Headers/X-Forwarded-For I thought it was that part I don't know because there's no clear explanation..