He didn't know how many others were imprisoned. The halls were lined with doors similar to his own, two double doors on either end. One to a stairwell, the other he believed to some sort of break room; But, he still had only the barest idea of how large the building was. From the samples he saw in the lab, Granger’s estimation as to captives must be correct - over ten, unlikely to exceed 20. A small comfort. 