According to AUTOSAR DEM SWS Document :
Healing of diagnostic events
The Dem module provides the ability to activate and deactivate indicators per event
stored in the event memory. The process of deactivation is defined as healing of a
diagnostic event.
Aging of diagnostic events
The Dem module provides the ability to remove a specific event from the event memory, if its fault conditions are not fulfilled for a certain period of time (operation cycles).This process is called as "aging" or "unlearning".
Few points to notice ( According to my point of view ) :
1 - Each one of them has a separate counter and a separate threshold, When the counting value meets the provided threshold, corresponding action is being taken.
2 - Normally, healing comes before aging.
3 - Aging resets the confirmedDTC bit in the status byte of the DTC. Healing just means we have an operation cycle in which the event status byte never had the testFailedThisOperationCycle bit set before.