There is no electronic link between the M9 camera body and the manual lens, because you are setting the aperture via a manual ring on the lens, rather than a dial on the camera that gets transmitted to the lens like other modern cameras, right?
Therefore the camera cannot know what you’ve set the aperture ring but, but it guesses what the f-number is set to using its light-meter and other exposure parameters. This guess can be wrong.
Here is a more detailed discussion:
https://forums.adobe.com/message/5281346
If this doesn’t match your situation, please post back what you feel is different.