Maximum number of concurrent sessions

I am trying to understand the maximum number of concurrent browser sessions that can be opened given a certain configuration in the Advanced Settings of my app. Currently, for my app I have the following parameters set up in

Max Worker Processes: 10
Max Connections: 2
Worker Load Factor: 50
Instance Load Factor: 100
Start Count: 1

I am currently under a Basic plan that supports a maximum of 3 instances.

With these parameters, the maximum number of sessions that can be opened happens to be 20. I will appreciate if someone could please walk me through how to get 20 from the above configurations. My expectation is that I would be getting 30 concurrent sessions not 20, given that there are 3 instances running and that each instance (given the configurations above) can handle 10 workers, each worker handling 2*50% = 1 session. Thus, I am not sure why/how I get a total of 20 sessions not 30. Any help in figuring this out would be much appreciated.

Thank you in advance.