Setting of the AsShotNeutral and ColorMatrix

Now, I want to create a dng file with my camera, and set the AsShotNeutral as follow:

1. I get the white balance ratio as GainR, GainG, GainB, and set the AsShotNeutral as: GainG/GainR; 1; GainG/GainB.

    For example, the GainR = 6508, GainG = 4096, GainB = 7609; the AsShotNeutral is [0.629379, 1, 0.538309]

2. The colormatrix is D50 XYZtoRGB as follow:

     3.1338561 -1.6168667 -0.4906146
      -0.9787684  1.9161415  0.0334540
      0.0719453 -0.2289914  1.4052427

Then I capture a dng file with my camera, and open the dng with the photoshop. It looks ok, however, when I change the exposure time from 1.40 to -1.40, the bright white become s light pink.