To have more control over how you Roster your Roles and Shifts, use the Default Settings.
Default Role Settings
When creating or editing a Role, you can set the default Staff Required and the Default Signup Limit for said Role. The default staff required is the mark you have to hit to successfully staff a Shift and the Signup Limit is the cut-off. These numbers are used as the default when creating a shift, however making changes to these settings from the Roles tab will not be reflected within any existing shifts.
You can edit the default Min/Max by selecting the Role from the Roles tab and choosing 'Edit Details' from the 'Take Action' button.
To give you more precise control over the Default Staff Required and the Signup Limit, you can adjust this on a Shift-by-Shift basis. This will override the default settings depending on what you choose for the Shift itself. For example, in the image below, I only need one Customer Service at any time during the chosen Shift and the settings reflect that.
You can edit Default Staff per Shift by selecting them individually from the Shift pop-up, and in bulk with the 'Take Action' button when working with the Scheduled Shifts or Scheduled Roles List views.