Parallax RFID Read/Write Module 28440

May I ask a stupid question?

In UberDude's code above (1st post), he shows the serial number of 2 of the tags he was using (they're commented out) 0800E28C60 and 0800D9E43E. Both of these serial numbers have 10 digits (5 Bytes) but he is only reading 4 bytes with the code, and the .PDF on the tag states that the tag's serial number is 32 bit (4 bytes). I'm lost...