Simple Mifare 10 digit explanation

Mifare cards will typically have a 4-byte UID. A customer system will convert the 4 byte array to an interger ( 8, 9 or 10 digit number) but in the words of NXP (see very first note in section one in the attached pdf)

Note: A UID is not a “serial number”, but a unique identifier. There is no recommendation how to turn the array of bytes into an integer.

The simple solution is to buy cards with a 7 byte UID. A 7 Byte array will translate to a 16 digit number. The access system with a problem will most likely truncate the number down to the required 10 digits.