Color setup in CT Pro 301b 20 beta

I am a little confused with the dialog and results obtained using the Color Setup function on a loaded CGATS file ( complete with spectro data)
I have a 300 patch file that is tagged with in a D50 . When I change the illuminant to D65 (cooler) the LAB data changes to indicate higher b values not lower and all the patches change to a warmer hue.
If I choose Illuminant A (Tungsten) the b values go lower, not higher. Any idea what is going on or have I missed something soomewhere.
What I ultimately want to do is calculate DE2000 values of a comparisom of the same file in two different illuminants.

ps. Ive tried the same file in the CT 3,0 version and I dont even get the option of color setup and it looks like the spectro data is not recognised