Scheduler - Workflows allowed to run simultaneously

[Jbone]

In the Scheduler, I am trying to set the number of workflows allowed to run simultaneously to 1. 
When I go into the System Settings it is set at 2. I change the number to 1 and click Next to page through the rest of the system settings. When I reach the end I click Done. When I come back to screen shown below the number has reverted back to 2. How do I get it to stay at 1?

Thanks

[Watermark]

Right now you aren't checking the box for allowing simultaneous runs, so it doesn't become a factor. If you allow simultaneous then obviously 2 is going to be a minimum since 1 isn't a simultaneous number. 

[Jbone]

Thanks for the reply Watermark, that makes sense. 
However, what made me question this setting to begin with was that in the scheduler queue there is sometimes more than 1 workflow running at the same time. For instance a workflow that is scheduled at 8:45 am is still running at 9:00 am and the workflow scheduled for 9:00 am starts running before the previous workflow is complete. 

It is my understanding that in this instance the 9:00 am workflow should not start until the previous workflow completes. This doesn't occur all the time, but I see it occasionally.