I just completed a simple 1040X amendment of a form 1040 personakl income tax . This return included a 

recovery rebate credit of $600 on the original return. This rebate was not carried forward in either column A original amount or columb C correct amount. I had to manually enter the $600 on line 15 Refundable Credits Other  and indicate Recovery Rebate in the space provided. I have tried three times to reach someone at ituit with no sucess so just be aware of this issue!