The party has just rescued 100 slaves. How many of them can conceivably enter a teleportation circle before the spell ends? It seems absurd to think all 100 can make it.
The teleportation circle spell description states that:
A shimmering portal opens within the circle you drew and remains open until the end of your next turn. Any creature that enters the portal instantly appears within 5 feet of the destination circle or in the nearest unoccupied space if that space is occupied.