Interest u/s 220(2)

As Per Sec 220(2) of the Income Tax Act, 1961, interest is charged on amount of outstanding demand raised by CPC/AO for the period beginning from 30 days after the notice u/s 143(1) given till the date of making payment of demand @ 1% p.m. for every month or part of month of delay period.

while in my case, calculating interest as per sec 220(2) it is almost double of the amount raised by income tax deptt on Income tax website.

If wrong please correct.  

calculation as per me =2 * amount of interest u/s 220(2) raised by deptt