p-value for panelists correctly identifying both sets

#1
We've been running the attached sensory analysis test at work for the past few years and using the attached "Chart 1" to determine the p-value. I would like to walk through the math that created the chart, but I'm not sure where to start.
For example, I tried to work out the case that 6 out of 10 panelists correctly identify both sets. According to the chart, the p-value would be 0.0197, or highly significant. This is as far as I was able to get:
Expected value = 0.25 (Probability of correctly guessing both sets)
Observed value = 0.60 (actual value in this example)
chi-squared value = 0.49
Significance level = 5% (assumed)

Plugging this into a chi square distribution chart, I'm getting a p-value between .1 and .9, which is completely different from "Chart 1". Where am I going wrong?
 

Attachments