I would say to check the oil level prior to the first engine start of the day. This ensures that all the oil has drained into the sump overnight and gives you an exact oil level reading. (car on level ground of course)
User manual says to check it with the engine at normal operating temperature, on level ground and after the engine has been turned off for five minutes.
I don't think the check function will work with a cold engine.
I'm assuming that yours is minus a dipstick the same as mine.
6.5L. I always do mine stone cold. Don't overfill it or you'll get a high oil level warning when the engine is hot. I've seen mine as low as 5L and it still wasn't asking for more oil.