Time cards are approved based on your grace periods. Grace periods tell the system how many minutes before and after the scheduled time do you want to generate an exception and be alerted.
Read this article on how grace periods are calculated.
You can change your grace periods via MANAGE MY DEPARTMENTS (department based rules, the default) or MANAGE MY SHIFTS (shift based rules).
If an employee punches in BETWEEN the grace periods the time cards is auto approved. If not, it will require approval.