Mercman is asolutely right. Outdoor space should not be calculated in the calculation of apartment floorspace, which is officially living space. It would be like including the area of a rear garden in the calculation of the floorspace of a house. It makes no sense. However, I have experience of estate agents including the area of a balcony (in my case 14 square metres) in the calculation of the apartment floorspace. I imagine if they can get away with it, they will do it - after all who is regulating or checking this.
I would definately recommend getting the estate agent to confirm this and also get the apartment (when completed, if not already) measured. An apartment that I was signed into buying was 20square metres smaller than advertised when completed, which is a significant difference!! We managed to get our money back as it comprised a fundamental flaw in the contract, but others I know in the same block were not so lucky. Some people didn't measure up until after they signed final contracts and moved in only to discover a large amount of missing floorspace.
Also, I would be cautious of measuring from floorplans. Often what is shown on plans and what is actually built is very different. That has been my experience anyway.