Respected sir/Madam i secured 509.5 marks in MAT Paper Based Test am i eligible...???

yes you are eligible

Balaji society prepares a common cutoff considering the CAT,MAT,XAT scores of that particular year.The gd,pi is going on.Do one thing,go for spot registration.If your score is above their requieremant,they will register you,otherwise they will simply tell you.This way you can save your registration