The bar graph on the left side of the window displays the percentage used for each frequency; the highest current percentage used is labeled on the top left of the graph. In you scenario, the highest percentage used for any frequency is 29. The access point's available frequencies are listed vertically across the bottom of the graph, from 2412 to 2462 GHz. The access point's channel 1 is 2412 GHz, channel 2 is 2417 GHz, and so on up to channel 11, which is 2462 GHz.
The bar graph on the right side of the window displays the amount of noise on each frequency. Noise is a measurement of the signal the radio receives when it is not receiving packets. Even in an environment in which the radio receives a great deal of noise, it might also receive a strong data signal.