If you're refilling after changing the oil and filter, then, as Ron said, you'll need to crank it over until the oil light goes out to ensure the filter has been filled. I tend to aim for just below maximum.
Then leave it for 15 minutes or so to allow any oil in the system to drain back to the sump. And, as Dukedesmo says, be wary of the manual; in the text it says tighten the sump plug to 42Nm BUT in the torque tables, it gives the correct figure, which is only 20Nm.
As Ron said, the oil expands when heated - I seem to recall the CoE is 0.0007 per 1°C (I remember that thanks to James Bond for obvious reasons!). So, 4 litres of oil at 20°C would become about 4.2 litres at 90°C.
Another reason for not checking it immediately after stopping the engine is the fact that it takes time for the oil to drain back to the sump from all the nooks, crannies, oilways and galleries that it reaches when the engine is running.
I would guess that you'd get the highest level about ten minutes after turning off the engine; most of the oil would have returned to the sump and it would still be hot enough to show expansion.
It can be difficult if you're on your own to hold the bike level to check the sight glass. My method, (working on a level garage floor), is to insert the paddock stand into the rear axle without lifting it. If the floor is level and the front wheel is pointing straight ahead, the bike will stand on its own perfectly level.
It's a bit precarious mind so, if that's too nerve-racking
just steady it with your left foot on the right wheel of the paddock stand as you bend down to check the sight glass.
