There is no real limit, but if you have more than 3200 cigarettes then you are liable to be asked by Customs to explain why you have so many and convince them they are for personal use.
For some EU countries (Bulgaria, Czech Republic, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia or Slovenia) there is a limit of 200 cigarettes that you can bring back without having to pay duty. You can bring more, but youll have to pay extra duty for them.
I'd ignore the sign, probably an old one.