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Hi Stephen! Thanks for writing with a great question! Campaigns have up to a 90% tolerance for duplicate content. This includes all the source code on the page and not just the viewable text. So if a URL is at least up to 90% similar in code to another URL, this warning will appear. Although the pages in question are may appear to be different on the front end, they are actually duplicates based on this percentage. We don't know what standard Google uses, but it's safe to say they are a bit more sophisticated than us - so you might be okay in this regard as long as you have a couple hundred words of unique text per page. Google won't say how much duplicate content is too much, so we like to be better safe than sorry. Hope this helps!