For a breakdown by SSID, you might have better luck trying the Client Session report. Or you can create a custom report definition to include just the portions from Client Session that are SSID based:
Session Data by SSID (List)
Session Data by SSID (Charts)
Summary
The summary will give you the unique clients count (designated as unique mac addresses). The SSIDs charts and graphs will reflect if the client switched between SSIDs at all, and give some rough ideas of the most used SSIDs monitored in the environment. You might even like to see the connection modes as well in case you're broadcasting the same SSID over 2.4 and 5 bands.