Your specific volunteer shift times are found in the MVP Portal in 'My Roles'. You can also see what discounted volunteer ticket you will earn after you complete your shift in the role description on the application form.
However, in General:
Half-day Shift = 6 - 7 hours
Perk = Discounted Participant Entry Fee of $40
Full-day Shift = 10 - 12 hours
Perk = Discounted Participant Entry Fee of $20