Had the chance to shoot my ColorChecker 24 chart using a Manual Exposure mode.

I used Spot reading on patch N5. The result is here :
https://1drv.ms/b/s!AkD78CVR1NBqlsJM1NJMBouJhQPcdg?e=CaNJID

There is a screen capture of the RawDigger main window.
There is a Histogram of the entire image.

Then I made a Selection of only the bottow row.
I made a separate screen capture.

I was expecting EV0 to be pegged on the 18% Reflectance of patch N5 but that's not how it works.
If I remember well, RawDigger calculates -3 EV from the max to locate EV0 (or something like that).

One questions, if I may.

I suppose there is a "reason" why the red channel is way "underexposed" compared to the green and blue channel?
Could be a "feature" of my camera?
Could be caused (to some extent) by the "overcast sky" lighting condition?

It is the same behavior as observed on my previous two experiments.

In this case, I got R: 626 G: 1666 B: 1730.

I recognized I did *not* made any white balance adjustments at the time of taking the picture.

This is interesting. Thank you very much in advance for your help.