I just found out that in some movies, for some reason the bottom part of number 9 on digital clocks is cut out. An example from Back to the Future (6 gets the same treatment):
I'd just dismiss it as them using a weird clock, but then, here are two examples where the clock used is a real clock model, and the real clock uses standard numbers - so this has to be deliberate.
Note that I got the movie screenshots off a discussion forum, so there's a slight chance someone is just trolling me, but that would be a very weird way to troll, so I'm inclined to believe those are real screenshots.
So, what is the reason for that? Is it some inside joke like Wilhelm scream? Or is that done to make sure the audience doesn't confuse it with some other numbers (in which case, why wouldn't clock makers do this too?)?