What is meant/implied by "じゃないんだからね"?


I noticed today, while playing _Grisaia no Kajitsu_ (English version, since my
Japanese is really bad), that when I click on a menu option while using
Michiru's voice to voice the menus, she ends her sentence with

> じゃないんだからね

(one example being clicking "Extras," which causes Michiru to say

> おまけじゃないんだからね

). I'm not entirely certain that she uses the ん sound, but it sounds like it
to me. It sounds as if she is telling me that there is no omake, but I feel
like I'm missing the importance of the "んだからね". She is supposed to be a
tsundere (well, a fake tsundere anyway), so that likely plays into this.

[Here is a short clip of her saying
it](https://drive.google.com/file/d/0B7ov93qPwGFpTmIydnVDcU1kVVE/view?usp=sharing)
(4 seconds, made with Windows 7's sound recorder), so that you all may tell me
that I terribly misheard everything and should give up on Japanese forever.

[I converted it to a
wav](https://drive.google.com/file/d/0B7ov93qPwGFpU1Ribm03dl9GaTg/view?usp=sharing)
(using online-convert.com), so it should play without being downloaded, I
think.




You heard it quite right; she is saying 「おまけじゃないんだからね！」.

Where you would normally hear something like this from a ツンデレ is in a scene
where she does something for a guy and then follows it up with
「べっ別に好きってわけじゃないんだからね！」 "I-It's not like I like you or anything!"

In my opinion, it doesn't really make that much sense in this context, but
saying 「〜じゃないんだから」 excessively is basically part of the ツンデレ trope, and I
guess they are just extending it to somewhere where it sounds completely
ridiculous for fun. She is basically saying "It's not like this is an extras
screen or anything!" or "It's not like these are extras or anything!!" or
however you might want to interpret it.




You heard it quite right; she is saying 「おまけじゃないんだからね！」.

Where you would normally hear something like this from a ツンデレ is in a scene
where she does something for a guy and then follows it up with
「べっ別に好きってわけじゃないんだからね！」 "I-It's not like I like you or anything!"

In my opinion, it doesn't really make that much sense in this context, but
saying 「〜じゃないんだから」 excessively is basically part of the ツンデレ trope, and I
guess they are just extending it to somewhere where it sounds completely
ridiculous for fun. She is basically saying "It's not like this is an extras
screen or anything!" or "It's not like these are extras or anything!!" or
however you might want to interpret it.

