Users Billing: 2 Users, that are not users, that I am getting billed for

I got a notice today that I was out of users. As I had 10 bought this confused me because I only have 9 people that are doing building on my team. When I looked at the billing users I see two users, Scheduled Workflow and Unregistered User, that I am being charged for. I know what Scheduled Workflow is (I run a workflow every night), I dont know what Unregistered User is. I dont think I should be being charged for either of these and I cant tell what the one even is.