The field "Total Volunteers" is a System field in Volunteers for Salesforce (V4S).V4S clearly states that this field should not be edited. When this field is edited any calculations related to "Desired # of Volunteers" and "# of Volunteers still needed" will no longer be valid.
Editing the Total Volunteers field DOES NOT change the Desired # of Volunteers and "# of Volunteers still needed" fields. These two fields are used within V4S Mobile to verify if more volunteers can sign up for a specific shift. Since the data in the two fields are no longer correct, there is a possibility that more Volunteers can sign up for the Shift.