Difficulty to enter Serial Number

I purchased this: ATI 2015 for PC - DE - PROMO-BOX 1 + 1. Since i have only one PC, the dealer cut off the Product Serial Number for the 2nd PC. What is left for me is Serial Number 1, consisting of eight blocks of 8 alphameric signs. I am supposed to enter the serial number after installation, but the field provided takes only four groups of my Serial number. As a consequence, I can not register the product. What am I to do???