IF you are talking about the option to fill out at the time of entering info for the GMAT, that part is optional and you dont have to bother about it.
Schools dont really ask you to convert. You send them your transcript and they know how to interpret it. They've dealt with thousands if Indian applicants over the years, and they know the standing of colleges in India.
Thanks for clarifying. I hold a undergraduate & post-graduate qualificaiton from India and wanted to make sure the process that I had to follow to have these converted.