Employees register their arrival and leave. Therefore, raw DAccess information collected from equipment (readers) only provides confirmation of employees placement at his/her workplace. Usually enterprise has responsible personnel with rights to enter corrections into system- justifying information on reasons why employees are not present. It is very responsible work connected to salary calculation- for that reason all changes are logged.
In reality correction are being entered at later date. For example, employee missed work on Thursday and Friday, but provided doctors note on Monday - in such case 2 missed working days are changed to sick leave when calculating salary. Same process is used for business trips, lunch breaks (if not clearly defined in internal rules), allowed late arrivals.
When the employee is present at work, his status and salary can also change depending on are the given hours usual workin hours, overtime, night work, work during weekend/holidays etc.
This way dAccess Reports module allows not just checking reports on time worked, but also enter basic information on work schedules, correct worked hours and control how the really worked time correlates to the planned one. The type of corrections and responsible employees are usually decided by internal policies of the enterprise.