The Home > RF Capacity page provides summarized client and channel information for traffic that occurred on your network over the last week. This page is updated after nightly maintenance has completed. The process goes over all the radios and determines the maximum client count and maximum channel utilization for each radio.
This page includes two sets of graphs. The top tables show the total number of clients that have connected over the last week (2.4 GHz and 5 GHz) and the percentage of these that were above the usage threshold. The bottom graphs show the number of clients that were connected during low and high channel utilization.
screen shot which you have shared
If you look at the channel utilization of the access-point radios you will see a "radio RX" and "radio TX" value. Those values show how much channel utilization that access-point radio is responsible for. When those values are low but the channel utilization is still much higher you run into something called co-channel interference (CCI). This basically means that other access-points in the neighborhood are using the same channel.
In above screen, I see AP radio channel is not busy, it is looing good.