I got a letter from the IRS saying my refund was reduced by $*** because of an error on...

I got a letter from the IRS saying my refund was reduced by $*** because of an error on child tax credit. I used the software to file my return. I stopped in my local branch for a *nd look. I was told their calculations were slightly different than mine, but I was correct about the issue of the child tax credit. I then called the IRS who was able to explain to me exactly what happened. She said that because the refunds must come out in a certain order (refundable before non-refundable) that I didn't use all of my residential energy credit carryover, and that was the reason for the difference. However, the software and the person who did the *nd look seem to think otherwise. So my question is *) who is right? *) if the IRS is right, what will happen next year when the software thinks I used up all of my residential energy credit?