Just because the R's cooling system is "sealed," that doesn't mean that there isn't some loss through the reservoir overflow hose, either as liquid or vapor. Everyone should expect some degree of coolant loss over time; the question here is how much loss is there and how quickly is it occurring. As noted by others, there are a host of variables which can affect the level in your reservoir: engine heat, angle of the ground where your car is parked, etc. Me? I'd watch it and see if the level moves SIGNIFICANTLY (more than you've indicated in the posting) week to week, or month to month, before worrying about it. Worst case scenario: you have to top off your coolant every few days while waiting for any parts to arrive at your mechanic.
It's not sealed to the point where the molecules of the components of the coolant cannot leak through the seals, especially since it's under pressure. It's not like it's hermetically sealed. I smelled coolant when I first bought the car but it eventually went away. Probably a leak at a connection where the coolant finally hardened. I had it happen on a hose connection on my after run pump on my MK4.