Bulk Voting - Which users are used to vote when bulk voting is activated?

I have bulk voting activated on my site and configured the permissions to activate when one of my 'fake' users vote on certain scoop.

The question is when the bulk votes are done, does it chooses randomly from ALL the users of the site for creating each vote or does it chooses from the "comma separated list of UIDs who will vote randomly the stories voted by the deciding users" in the autovoting configuration?

IF it chooses randomly from all users, is there a way to make bulk voting only with MY 'fake' users and not from real users of the site?

Thanks in advance!!!