Clanad, perhaps this will help you to understand rowanwitch's comment:
"Litotes are a form of understatement, always deliberate and with the intention of emphasis. However, the interpretation of litotes can depend on context, including cultural context. In speech, it may also depend on intonation and emphasis; for example, the phrase "not bad" can be said in such a way as to mean anything from "mediocre" to "excellent."
The use of litotes appeals specifically to certain cultures including the northern Europeans and is popular in English, Russian and French."