For most companies, this is set under
Manage My Business » Business Settings » Manage My Departments
Select a department to edit and at the bottom, you will see the grace periods and length of meal/break.
Other companies that use shift rules will see it when they edit a shift under
Manage My Business » Store Rules » Manage Shifts
Grace periods can also be adjusted per employee as needed by going to Grace periods defined in employees’ profiles overrides his/her department rules.