To explain what happened, Puffer does not "kick out" existing connections even when the number of concurrent viewers reach the limit. A session can be disconnected from Puffer for many reasons, e.g., your network has a temporary hiccup, or your browser tab is put in the background and goes inactive. In these cases, Puffer server stops receiving heartbeat messages from your browser and considers the connection timeout (we understand our check of heartbeat messages is a bit stricter than, say, YouTube, due to an intentional design).
Sorry it happened to you, and I understand it can be frustrating. Hope you can return when we are not at the maximum capacity!
Best,
Francis