The beginning to 'knowledge' about what you're posting here is to know that doubled dies are NOT 'errors' - they are 'die varieties' which is a completely different animal altogether. And it's not just a matter of semantics - there are a vast number of people who collect one or the other but not both, and anyone who calls all of them 'errors' because they don't get the difference (or don't care) just SCREAMS 'rookie'.
I focus about 99% of my coin energy on die varieties because I personally don't like error coins. It's a personal taste thing, definitely, but having someone just stroll in and call doubled dies 'errors' just strikes a note...that's all. I'm certain you intended nothing at all by it, and I'm all-in to teach you the difference so you'll know.