As supplement to your explanation I can tell that the bars shown are the variables confidence interval. If only one part with two elements are tested then the bars shows the confidence interval for each of the elements. If the two bars don’t overlap then there is a significance difference on a 95% significance-level. Google write at which significance-level the results are significant, but the normal level is 95%.

For further reading http://www.statpac.com/surveys/statistical-significance.htm

Thanks for the programmer focus. As a number-nerd it is great to upgrade that