The easyiest way is to look at one of your existing cards or fobs.  The numbers will tell you all you need to know.  Take a look at the picture of the card below.  The numbering on a Kantech XSF ioProx fob will be the same.
It's really that easy.  If you have further questions, feel free to reach out to our technical support team at 970-682-0765.
Have a look at our Kantech XSF ioProx 26Bit Credentials
For much more information about the Kantech Extended Secure Format CLICK HERE