What CATS accepts as an input depends on how the attendance types are configured. You can configure an attendance type (named suitably to indicate that it is not paid for but only recorded to show the employee’s hours; e.g. extra hours) in T554S with a valuation rule. This valuation rule should result in zero payment. These hours are recorded in CATS or in PA30 for the purpose of showing the employee’s total attendance hours in a day.
You can also configure the CATS profile to show the normal Planned working time from infotype 7.
Hope this helps. If you need more info, you are welcome to ask.