To add to Keiths excelent instruction set, although I'm sure he missed a bit ...
The oil on the 660 motor naturally runs down into the bottom of the engine, that gravity thing. When the engine is running it pumps the oil into the header tank and this in turn is pumped/flows back into the top of the engine. The Scavenger pump runs a little quicker than the oil is drained from the tank, so this is why you need to run the bike before taking a dipstick level. It's called a semi-dry sump.
In practice, the best time to check your oil is after a ride, just after you stopped the engine.
What you know have, probably, is 300ml more oil than you need...., but best check it. There are conflicting reports of what happens when you have excessive oil, it's not something that ever bothers me too much