Ok more details to the situation.
I was travelling in a new aircraft type I havent flown before.
First it wasnt planned to be a training session but after takeoff we decided we might as well do some training anyway when we got the time.
This is the same situation as you fly two rated pilots and one person is flying the first half and the second one flies the second half.
It is also the same situation where you have two sets of crew members on board a commercial airliner. During the flight they switch crew members and the first ones go to bed or sit down to sleep. How do they log this? They are only flying 50% of the flight and 50% of the flight you are for example sleeping.
It must be the same problem. What do you put in the block boxes for such a flight?