What is the minimum number of doctors that could be at Souderton?

Hi, for question 3 I am confused as to why the minimum number of doctors is not 1. I used the hypothetical from question 1 to set up the question, and then tried to test if I could move one of the doctors to R without violating the rules. So first I had S: KL and R: JNOP. I moved L to R and did not see how this violated any of the rules, so I am unclear as to why this would not be a possibility