Was there a penalty on your 1040 line 38? The penalty is just an estimate so it is possible for the IRS to recalculate it and send you a refund or a bill for more. If line 38 is blank you might have checked a box to let the IRS figure it for you. Nothing you can do about it now.
You can go though the 2210 penalty and see if you come up with less. Go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties.
