Datacolor User to User Support Group.

This should be a real simple question and my appologies if it has been answered in the past (I did a search, but didn't find it)...

What would be considered an acceptable range of readings for measuring the white calibration tile.

I measured mine and got L=90.40, a= -0.98 b= -1.09 (Density 0.11).

Then I cleaned the tile using a paper towel and Sparkle Glass Cleaner (like windex but is pink rather than blue).  

I measured the tile again and the "b" value seemed to have changed quite a bit.  The new values are L= 90.67, a= -1.04  b= -1.59 (Density = 0.11)

Are these values within acceptable range and did it get better or worse after cleaning?

Thanks,
Rick