Nikon D5 - Correct Exposure in Camera and Import screen, Gets "Corrected" when Preview is generated

When importing Nikon D3/D3s photos, It never happened, But it happens with Nikon D5 NEF (RAW) Files: I shoot, If the scene is under exposed, I correct the exposure (Manually to the right value using ISO/Shutter, Not using exposure compensation.

I arrive home, Move the NEF (RAW) files from the card to my Mac. Then import them in C1: In the import screen shows the NEF files, Correctly exposed. But when I hit "Import" and they start being imported, Generating previews shows the images as under exposed, As the scene looked originally. If I click "Auto Correct" the exposure slide goes 1-2 stops up, As I did when changing the in-camera exposure: ISO/Shutter... So all of my collection has +1 +2 exposure slide values, Sometime also +1 +2 shadows slider.

I thought it might be something with ISO invariance, But I think NIKON D5 is not an ISO invariant camera.