If you want to specify when an employee is considered early or late to their shift (a grace period) you can do this by going to Settings --> Scheduling and updating the Early/Late Settings option:

If an employee punches in or out within the grace period you have setup, then no early/late alert will show on their time card.

If an employee punches in or out outside of the grace period you have setup, then an early/late message will be displayed on their time card stating whether they were late or early and will also show how many minutes from the original punch.