You can find their criteria for what they mean by ban on the FAQ page: https://pen.org/book-bans-frequently-asked-questions/

It's probably too long to quote here, but it's a very unique definition that seems worth taking into consideration when you read their other material.

It's ironic seeing The Handmaid's Tale on the list. Sad too.

Reading this you would have no way to know that there had been any book banning on the other side of the culture war at all. If your bubble is strong you may be wondering what the heck I could be going on about. In my bubble the practice looks vaguely symmetrical.