Why do some people say "amen" twice? [Spirituality & Religion]

Same reason a lot of not-praying people say, "All right. All RIGHT." or, Yeah, yeah, yeah or Okay. Okay!

Emphasis.

In case God doesn't hear them the first time

It's merely an emphasis on the undeniable truth of a statement to follow, or following a statement. Some say Jesus used it at the beginning of his sentences, and often twice for emphasis.

What kind of church is it?

sometimes i get so caught up in my prayers when praying with another that's double and triple amend are the equivalent of wow, bringing me back to reality. some times I have an out of body experience and the words are not my own. not speaking in youngest but rather the holy spirit guiding my words again the series of amens grounds me in reality.

I don’t know and I don’t know.

The only real reason someone would say that if the one they are responding to has made two points that the responder is in agreement with..

But i would say someone heard it being said and thought.. hey thats cool.. And decided to do it.. I have not heard it myself.. I am Australian so maybe it's just something you hear in your country?

So they can get extra God magic maybe.

Do they?