Board Thread:Movie discussion/@comment-28149253-20160407075912/@comment-24136096-20160407192739

Assuming that they had 8 to begin with, the way it's worded makes it seem like they had 7 already in the pen, and when the Big One was brought in (making the total now 8) she killed 5 and gained control of the other two through fear.

The Big One was already part of the same "batch" as the others, but was simply introduced to the group last. In zoos you don't just chuck all your social animals into the enclosure at once. They are usually put in over the course of a couple of days, allowing time for each one to get used to its surroundings and learn its place in the hierarchy.