"Not part of this thread"

[mrjam2jab]

I noticed something today.

In an existing thread I multi quoted two posts and clicked reply. Below my text box I see this:

You have selected 1 post that is not part of this thread. Quote this post as well, or deselect this post.

I went into another thread and clicked Reply at the bottom of the thread without quoting anybody and now under my text box I see this:

You have selected 3 posts that is not part of this thread. Quote this post as well, or deselect this post.

What does this mean?

[Emptymag]

Is it possible you clicked a multi-quote button elsewhere, then forgot, or decided not to post in said thread?

Maybe it remembers it when you click reply in another thread.
I've not seen/heard of this before, but that's not to say it doesn't happen.

[mauser]

Maybe it's the time travel thing we've been seeing with posts being out of order, as in quoted posts appearing before the original post.
You must have been anticipating quoting other posts after you were done with those two.