Why do you thin kit is a problem?
Did the documentation indicate that has only one drive letter?
If the boc was already open when you bought it, somebody else had made it into two partitions.
It is not necessary to do any modifications either to the sea gate firmware or the Windows software. If the documentation indicates that the drive should only have one drive letter, then call the vendor ans ask for a rerun or refund.
Please provide the exact model number and somebody here, maybe me, will find the documentation and see what is normal for that product.
Some SeaGate drives do come with two partitions, but without the model number I am not sure about yours.