A volunteer year for an organization runs January to December. This is specified at Config > General by entering 01/01 in the Start Date of the Volunteer Year field:
Volunteer Robert Hernandez has 2 time sheets on his Volunteer tab:
Photographer 02/01/18 for 15 hours
Crowd Control 10/12/18 for 11 hours
Let's run the Time Sheet Report for the last quarter of 2018. This would be done by setting a specific date range of 10/01/18 - 12/31/18 on the General tab.
The Total as of Start Date shows 15 hours as the Photographer time sheet instance happens between 01/01/18 (volunteer year start date for this year) and the start date of the report 10/01/18