Whenever there is a new post, it bumps to the top. Forum rules state that you are to bump your own thread only once in a 24 hour period.
As I understand it, that 24 hours also includes posts by other users. So, if someone else "bumps" your thread by posting to it, then the thread is eligible to be bumped again 24 hours after that last post.
Since Gullwing posted today at 11:19 AM, the thread would have been eligible to bump tomorrow, at the same time. Even if Gullwing hadn't posted, Joe221's bump was still too early. Now that I've posted, Joe221 can bump the thread after 24 hours, unless someone else posts.