Go into a forum and go to the screen used to create a new discussion.

If the user drags in more files than than the maximum number of attachments (max attachments is in the forum settings) a random subset of files get attached. If I am a teacher and I have 2 documents (say, the exam location announcement and the practice exam) to distribute to my students but I'm only allowed 1 attachment its unlikely that I'll say "ah well, that'll have to do" when only 1 of those documents attach while the other vanishes. We're just forcing the user to then delete any files that did upload before starting over ie putting those files into a zip then uploading that or similar.

We should either accept all of the files, or if we can't, then display an error and reject the whole lot.