You have the ability to create custom absence reasons under your Account Settings.
Click the Edit button to edit an existing absence reason.
You can edit the name or code.
Click Add Session Type to create a new absence reason.
Type in a name and code.
How Do I Use Absence Reasons?
Your Session Type Name will appear in the attendance dropdown menu in each session.
Your Session Type Code will appear in your attendance printout. Here's an example of a month with one absence reason logged: