Google doesn't care. Plain and simple, if a HUGE percentage of your website is duplicate content then you'll get penalized. Taking a full 10k words and having a extra 40k unique words would have you see no penalty.
The duplicate content penalty hits much harder for websites that have the same pieces of content indexed more than once within the search engine as a way to manipulate rankings/rank for multiple keywords with just 1 article by spamming it.
Otherwise, so long as your website is just copy paste from other sites you'll be fine. Afterall, look at almost all these news/tabloids sites, they have a high density of duplicate content and they still do well.