I've seen this close reason:
But if I click on it, I can only select Philosophy Meta. When should I use this option, and when not?
This vote reason is there to automatically migrate questions to other sites. If you click on it, you will see a list of options.
There are simple rules:
At the moment only Meta is listed in the options. That does not mean that if you want to migrate a question to Hinduism (e.g.), and it isn't in the list, you should just select Meta. It doesn't make sense to migrate the question to Meta, because it's off topic here (most of the questions on topic on Hinduism are off topic on Philosophy Meta). So, again, in this case you go back and leave a comment and potentially flag the question for moderator attention.