Probably very little if any. Most of his other posts that mention promising substances (e.g. Zembrin and other nootropics) like this one[0] don't even include links and if they do I believe they are usually stripped out but I didn't find one with a link easily to confirm. I'm guessing he just included it as there are multiple different brands for this one.

0. https://astralcodexten.substack.com/p/nootropics-survey-2020...

There's no referral link in this post, he's not profiting from this and he's written about many different treatments.