Ah, sorry, I assumed they contributed 8% to PHP just like they've asked WP Engine to contribute 8% (of their revenue) to them.

They are referring to the dispute between Matt Mullenweg / Automattic vs WP Engine.

Mullenweg has been demanding 8% of WP Engine’s revenue, access to their books, and the ability to direct their staff on what to work on. For context, Mullenweg is maintainer of WordPress and WordPress.org, and CEO of WP Engine’s direct competitor, Automattic. The dispute has turned very nasty and included a lot of unhinged behaviour from Mullenweg. WP Engine is currently suing him for a bunch of things, including extortion.

davidandgoliath is basically saying that if Mullenweg thinks he is owed 8% of WP Engine’s revenue, presumably Mullenweg is donating 8% of Automattic’s revenue to the PHP Foundation, making their revenue only ~$5MM/yr. Obviously Automatic’s revenues are vastly higher than that and this is just a tongue in cheek way of pointing out hypocrisy.

"had annual revenue" at this rate given their legal troubles

Revenue is not profit.

While the 8% is probably a dig, the donation of .06% of revenue is going to be a much higher proportion of profits. No idea what their profits or margins are (a quick search does not provide useful info)