Why interest rate changed in FD rates for 6 months 1 day and 6 month 2 days in IDBI bank ?

I was thinking of opening a FD in IDBI bank.

I looked on the interest rate provided by them on this link.

http://www.idbi.com/interest-rates.asp

What I did not understand is that why they have a different scheme for 6months 1 days?

Bcoz anyone who will wants to book for that can go for 6 months 2 days. and earn .35 interest more.

Why they make it differently?