I find Microsoft Word's spell and grammar checker leaves a lot to be desired.
The below image is a screenshot of the stats summarising my last twelve months. It appears I've checked* 842,279 words. In a year.
All seven Harry Potter books: 1,084,625
Lord of the Rings: 455,125
Oliver Twist: 155,960
20000 Leagues Under the Sea: 138,138
Nineteen Eighty-Four: 88,942
Charlie and the Chocolate Factory: 30,644
* Checking is different to writing. In other words, I may have checked the same content twice. Or there was a technical fail.