Person B is saying that he has directed a couple of horror movies, but that he is not really a director. "Not unless" means "no" except for a particular condition indicated by "unless".
Student or Learner
I have some difficulties in understanding the meaning of "not unless" in the following example which is a part of a movie:
A: oh, you are a director?
B: (Laughing) Not unless you're talking about a couple of horror movies.
The point is that after this conversation it turns out that Person B is no real director and is actually a song producer.
So, what is the meaning of "not unless" then? Does person B mean that he's made some horror movies?
In that context, "Not unless" could be replaced by "Only if".
- So you're a director.
- [You can say that], only if you include/count a couple of horror movies.
If, in your opinion, directing a couple of horror films makes me a director then yes, you can call me a director.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.