I called the Sandisk rebate center (Talked to Laura) and inquired about the last 3 digits of the upc codes. She told me that they look at the receipts and it must say "Extreme III" for that item and not to worry about it.
I did ask if those last three digits were used for production reasons and she had no clue.
I too got my cards from Adorama and I wouldn't worry about the codes. Adorama name is listed on the rebate form and Sandisk should honor the rebate.