That is strange, Key On Engine Off should read either 70% or 30% (depending on the meter).
I wouldn't pay much attention to readings with engine running until the 30 or 70% reading is achieved. That is the first step to know whether the computer is OK (I think).
May be an expert like stevebfl will provide his always "on the money" advice.
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car