Where does the UniqueId parameter in PreLogin come from?

Hello everyone, I am currently working with a class of type AGameModeBase and am overriding the following method:

FString AGameModeBase::PreLogin(const FString& Options, const FString& Address, const FUniqueNetIdRepl& UniqueId, FString& ErrorMessage)

But I am not sure where the UniqueId parameter is coming from. I know that the Options parameter can be passed when calling UGameplayStatics::OpenLevel on the client side. However, is there a way to pass a unique id as well through OpenLevel or any other method called on a client trying to connect to the server. Currently I pass a unique player id via the Options parameter which works fine, but I was wondering how, if possible, I could do it with UniqueId?

Thanks in advance for any help provided.

This is a super late response, but I eventually found out that anything to be passed from the client to the server should be done through the Options parameter when calling OpenLevel. The UniqueId parameter of the PreLogin function is a random value generated by Unreal Engine and should not be tampered with.