Hi Vishal, 

Thanks for A2A!

Generally some applications ask for your percentile or score directly while some others will ask for your application number of the relevant examination. In case 1, where they ask you your score, if you have filled the application with a score that score will be take. Sometimes you maybe given option to update your scores also.

To my knowledge, XUB asks you for the application number of the relavant examination. In this case, the best score is considered because the score will be released bu NMAT by GMAC and your best score gets autonatically updated in the database. The system will pick that score and give for consideration by XUB.

All the best. 

Hope this helps.