It seems you don't know much about the IGG structure? I'd highly recommend spending a few months researching just what the platform is and what makes a successful one.
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Once you reach your goal, you've funded. Then you supply them with a few higher goals known as Stretch Goals, these are things you promise to make even better about your project in exchange for more money.
Also, yes you can ask for too much money. If you were to task 15k for a comedy short film, I'd most likely question if you even know what you're spending the money on. As well if you asked anything above that I'd question you. First IGG? I'd be concerned if you went double digit into the thousands at all. The 1-3k region makes a perfect first campaign. From there you can jump to 5-10k. Heck if you make an amazing project out of that 1-3k campaign people will be much more likely to back you for an even higher goal. Possibly even a 50k feature if you really prove your worth to them.
On an unrelated note, Kickstarter is a much bigger and better platform. People have much more trust in the projects that come through there. Somewhat because a majority of people have feelings against Flexible Funding.