Contains the four low bytes of the value 100,000,000,000 (100 billion).
The maximum number of digits that we can print with the BPRNT routine is 11,
so the biggest number we can print is 99,999,999,999. This maximum number
plus 1 is 100,000,000,000, which in hexadecimal is:
& 17 48 76 E8 00
The TENS variable contains the lowest four bytes in this number, with the
most significant byte first, i.e. 48 76 E8 00. This value is used in the
BPRNT routine when working out which decimal digits to print when printing a