When a teacher marks a student as absent, they also have the ability to write a comment as to why the student was absent, if they know. These comments allow it to be easier for site staff to verify the absence reason and update the attendance code from an unverified code.
To run this report in Infinite Campus, go to the Index > Attendance > Daily Attendance. There are two options for this report, the Summary Report and the Caller Report. The Summary Report is what you will want to download to view all absence comments provided by teachers for each student that day. You can then use those comments to update the unverified absence code to a code that matches the true attendance reason.