Fill All is not Manual meeting creation - it is automated, but on a smaller scale and focused on one person or company.   It will use the same approach as general automation, trying to prioritize by rankings - and is subject to any limits or maximums you apply.

Click on More in the second level of the navigation bar - and pick Fill Requests. You will be offered the chance to select how many meetings it creates. If you want it to do as many as possible - then pick All, and hit submit.

The system will try to allocate meetings as best it can. It will look at the Request Ratings and try to prioritize the most highly rated requests - subject to the other side not Declining the request nor rating it so low that the rating value is negative. It will not try to schedule group meetings. It will only schedule 1x1 meetings - though it will put people from the same company into meetings together if selected.