Larry - Having not used NG before I can only speculate. But, I would say that the 'graphic' doesn't update if you configure both radios to use 5GHz. This could simply be a nuance in the GUI.
Start by completing your configuration and pushing it to the AP in question. You can then SSH into the AP and run the 'show acsp' or 'show interface' commands to see what channels have been assigned to the radios, alternatively you could use the monitor tab with NG to view this (you may need to add these columns.