In standard SAP time efforts are posted as confirmation with transaction IW41 to the order. The times are taken over from the App. This can be overruled per activity type e.g. by setting fixed values. Entries posted with CATS can also be defined as presence- / absence type.
Options ‘absolute’ and ‘fixed’ in the ‘Time posting’ field should only be used when time is posted to an order confirmation, not CATS.