2006 Saturn Relay Van automatic tranny SATURN not Dodge

Question

The mileage display box on the dash shows 96,000 miles +, and underneath that in the same
box is a smaller display of the numbers: B 400.2 which escalates as the vehicle is driven.
It goes up in .10 increments every 1/20 of a mile or so. By the time I had driven 10 miles,
it was at B 423.2. What do these codes mean?