CA INTERMEDIATE balance group registration

I have to register for the balance of CA INTERMEDIATE to appear in may 2019.
When I was registering for balance group I.e. group 2 , it is showing Rs. 13000/- .
I have already paid Rs. 13000/- at the time of group 1 registration.A s the total amount is Rs.18000/-of both groups. What should I do ?
Please reply me as soon as possible.

         Thank you.