Limits & Geofencing
The rules area is pretty straightforward. For entry-based ballots, you can assign the maximum number of entries that one contestant may enter into the ballot. You can also allow each user to vote up to X times on your ballot.
The sign-up restriction lets you hold "curated" ballots on entries/individuals that only the event admin can enter into consideration.
Geofencing is great for live events where you wish to prevent voters from sharing the ballot online to get more votes for a particular entrant.