Ads matched with content!

Just created an account with Google adsense and trying to figure out how to match ads with my content. I read their FAQ about it, added channels where included description of the content, when I add ads to the site, ads display completely different things, things that do not match my content.
It has to work like that from the begging and only after a while ads will catch content of the page?
Thanks for help folks!

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