Int on due amt paid on 02nd sep,but due date extended to 7th

That's because interest on refund is also paid and interest is paid on refund even if it is below 10000. It does not have amt restriction for interest on payment of refund. Such restriction clause is in case of payment of advance tax. 

Sry It is not Sa but adv tax. Yes my advance tax was more than 90% and the ITR for that year was still calculating the Interest u/s 234B and C.  I paid a little more.

In 143(1) info sheet the Int calculated  showed nil and i got xtra refund apart from int on refund u/s 244.  hope this claifies

Now, for our case IT dept automatically calculate and if any amount paid additionally, they will issue refund.

Evven if the utility calculates int. Pay the int and take tax credit.

when you get Asses Info under 143(1).you will come to know