How to calculate interest on tds default

Hi

I received default notice from tdscpc my query is i have deducted tds 10000/- date of deduction is 30/4/2012  and date of deposit is 16/05/2013 and date of order pass from cpc is 17/06/2013 they demanded 2100 interest and now i am depositing the interest so how to calculate the interst should i calculate on 10000/- or should i calculate on 2100 for u/s220(2). please suggest.