XF 2.2 Question about attachment thumbnails at the bottom of threads

[CBI Web]

I use a number of images in tutorial threads in my forums. I notice that some images show up at the bottom in a list of attachments. But not all of them show up. For instance, in a thread that contains 10 images, only 4 show up at the bottom.

So what makes those attachments show up but not the others? I'd like to prevent it from happening.

 

[Paul B]

If the attachments aren't inserted into the post as thumbnail or full size, they show like that.