The threshold of members required to be on call at any time can be set from within the On-Call Planer. Navigate to the [On Call Planner] in the [Operations] tab then select [Defaults] on the right hand side. The required member threshold can be updated by the drop down menu at the top of the page.

You will see a notification on the Dashboard as your team’s number of off-call members nears and surpasses the set threshold.