The Absence Export File will look at when the last absence export was run for the data selected (ALL or SCHOOL) and pull though all the absences since the last export on this particular report.
If the export hasn't been run for a while, or if it has previously been run for individual schools and is now run for ALL, the file will have a lot of information and may be larger than usual.
To check when the export has been run and if this has been done for all schools or individual schools:
Click Payroll, then Import/Export.
Click Absence Export.
You will see a list detailing when each export has been run and for which payroll.
Click Export on each line to view the file and see which employees have been exported.