To ensure you have the correct number of volunteers for your event, be sure to clearly state the minimum and maximum number of signups for your event or role.
For Shifts:
Click Add Shift:
When you have finalized with 'Create Shift' you will see it appear within your schedule - stating the #/# (actual/maximum) number of volunteers.
For Gatherings:
Simple state the minimum and maximum number of people within the Permissions tab.