Maybe a stupid question

I have yashica fx-3 camera and I have understood that the asa should be the same as the iso in my film. I have vista 400 black and white film but there isn’t a 400 setting on the disk. I am a total beginner.

I have yashica fx-3 camera and I have understood that the asa should be the same as the iso in my film. I have vista 400 black and white film but there isn’t a 400 setting on the disk. I am a total beginner.