Back in the 80s I had a part-time job with the publisher of American Express calendar books. I spent a few months as a proofreader and then a month as a copyeditor. It was good training. That stuff is basically boring, so catching errors required the closest attention. It was my job to catch mistakes.

I notice in recent years, mostly in the last couple of years, I miss stuff I never would have missed before. I think it's age. I leave whole words out sometimes. It's disconcerting. It's a privilege to age (a lot of people don't get to do that) and it is also a humbling experience :)

As for olive oil. I only buy top brands and virgin. As a grandchild of Sicilian immigrants and niece of a man who used to make his own olive oil, I don't skimp on the stuff. Cheap olive oil simply doesn't cut it for Sicilians.

I'm glad you caught those errors. As nancybriti1 said, I find typos in books all the time.