As to the buttons I am not sure what you mean, you mean the iso1 and iso2? you know that if you press both at the same time you can put a "factor" so that the meter under or over exposes always, right?
Yes, I meant that. But if I remember well the correction with 2 buttons pressed at the same time was then valid for both the spot and the incident measuring? (I sold it some year ago.) My 508 had correct incident measuring, incorrect was just the spot .