Amended returns can be very confusing!
The reason you owe taxes on the amended return is because on your original return you claimed a
deduction for your step-daughter that you shouldn’t have claimed. So, in effect, on your amended return, your
income and therefore, your taxes have increased.
If you originally had a refund and now you owe, the net of the two numbers
is what you would have received or owed if you had filed the original return
without claiming your husband’s daughter.
