FS35Pilot - nothing wrong to ask here. You will always find someone to answer a 'proper' question properly. Even if it's coming out of FS world, and related to ATC.
For additional understanding, how complex airspace and FL allocation design is working have a look at the link from skyguide:
http://www.skyguide.ch/fileadmin/use...F28JUN2012.pdf
You will see small grey writing near those route lines. EVEN, ODD... Sometimes different than 'normal' orientation. But even that can be subject to ATC tactical decisions and planning.
Hope that helps.