Avoiding Capital Gains...

I'm selling my primary home and live in it for less than 2 years. Good thing that there is Reduced Maximum Exclusion of the gains (you can find this in publication 523). My question is...when I file my gains do I need to specify of give my primary reasons why I qualify for the Reduced Maximum Exclusion? How do IRS track your reason of selling the house and if you qualify for the RME. Thanks for your response.