Well at least 50% of that % is me forgetting which is justify-content and which is align-items...

Words are hard

7.6%

this number is public: https://css-tricks.com/thank-you-2021-edition/

total traffic 88m, flexbox is 6.7m of that. speaks to their deep bench tbh.

That and the grids article are probably the most used bookmarked articles I have perused.

I bet it is in the millions. I help manage some sites which have CSS tutorials on them, and even if the article is about something like "How to use the CSS counter() property" - if you have the words "center" and "div" mentioned in the article, Google Search Console will report impressions for that article with keywords like "how to center a div". Funny!