The connection count on pricing plans indicates the number of concurrent connections allowed. For an explanation of concurrent connections see What are concurrent Channels connections?

A connection is counted as a WebSocket connection to Pusher. When using the Pusher JavaScript library a new WebSocket connection is created when you create a new Pusher instance.

var pusher = new Pusher('APP_KEY');

Channel subscriptions are created over the existing WebSocket connection (known as multiplexing), and do not count towards your connection quota (there is no limit on the number allowed per connection).

var channel1 = pusher.subscribe('ch1');
var channel2 = pusher.subscribe('ch2');

// All done over as single connection

// more subscriptions
// ...

var channel 100 = pusher.subscribe('ch100');

// Still just a 1 connection

If you want to know common reasons why connections are higher than expected, please refer Why Am I Seeing More Channels Connections Than I Expect?