We are a small shop with only 8 agents.  All agents are set with a with a rank of 1.  Take the following scenario. 

We open at 8:00AM.  By 9:00AM all agents have handled 10 calls.  One agent goes on break at 9:00AM for 30 minutes.  When she returns at 9:30, all other agents have taken 15 calls.  As soon as the agent that was on marks themself as available, they get the next 5 calls that comes into the queue (to get her to 15 calls).  After that 5th call she takes, the calls start to rotate the agents again.