Dashboard MPG Issue???

I drive a e92 330I 07 plate and I have recently noticed my average MPG on my car on the dashboard always says 99.9mpg and doesn't move however you can see i am average 25.6mpg on the i drive system but remains 99.9mpg on the dash board anyone know why?



The MPG that measures it constantly as in the real time one is working fine where it changes all the time etc.