Former ISC student here -
No, there's shockingly little correlation between your current studies and the GMAT; unless you're a natural at either GMAT Quant or GMAT Verbal, you may be underestimating your prep time when you assume 180 hours. You may be able to get to 680/690 in 100 hours if you're good, but the curve gets considerably harder when you cross the 700s. Consider 400 hours of rigorous effort before you begin. Also, I use the "GMAT" qualifier for both Verbal and Quant because it's markedly different from what you're taught at school. I topped the country in ISC English when I graduated but had to start from the beginning because of how different GMAT Verbal is. Of course, I was 8 years removed from any schooling experience, so you'll have an edge, but only a slight one.
However, this is a moot point. If you're taking the GMAT for your MBA, you have at least 6-7 years before you have to worry about it. Top MBA schools look for much more than your GMAT score. It's great that you're thinking about this at such a young age, but I'd advice you to do some research and start building a compelling story [profile] that sets you apart. (Fair warning: As an Indian Male, you're part of an over-represented demographic, so you REALLY need to set yourself apart to impress the top schools. Good news is that time is on your side.)