Every year I have "duplicate" clients in Lacerte due to amended returns or superseded returns.  When I proforma to the next year, I only select the amended or superseded return.  No need to proforma the original return.  For example, I change the client number by placing an X at the end for an amended return.  I then proforma only the client number with the X.  

Lacerte brought over both of your clients because you probably selected the entire list.  You can exclude clients that you don't need next year.