Custom server access URLs - How it works?

Hi

Does anyone know how the URLs are used specified in “Custom server access URLs”?
I’ve two URLs published but as I can see, only one of them are used. Don’t know how it works.

Example:
https://plex.mydomain.com:443,https://plex-cloud.mydomain.com:443

It seems not to be relevant in which order I put the URLs in the field.

Edit: Nothing found about this here: https://support.plex.tv/hc/en-us/articles/200430283-Network

Regards