README edit

README.md

@@ -2,7 +2,10 @@
 
 
 This runs a web app where /`lang`/`instance`/`user`/`hashtag` returns an iframeable page with
-of all posts by a matodon `@user@instance account` that contain `#hashtag`
+all recent posts by a matodon `@user@instance account` that contain `#hashtag`
+
+This is derived from the corresponding RSS feed (that's why we only get recent posts).
+I counldn't find a simple way to get this information via "proper" mastodon API, so I used RSS (like boomers do 😉).
 
 For example: