Raigeki

Is there any way to know which one parts of video will be showing on youtube as thumbnails? Or u think they choose them completely randomly?

Mostly when i add audio for example 5 minutes long, on that program its shows like 10 minutes or something like that. Tried to add same audio to windows movie maker and it was okey, but in camtasia studio audio files too long as it should be. What's the problem?