Thanks. I had some idea how the steps differed and how to calculate Y, and this helps clarify everything I was missing, but I'm still kind of curious as to how accurate the chart is compared to the theoretical L* values.
If someone could post the L* (the L value in Lab) for the darkest, lightest, and middle patch then that would be extremely helpful. (For example, is L* on the middle gray actually 50 or is it more like 49.4961? Does it even matter? Maybe by the time you get to the darkest one it does if it's much different than 25.26.)