Both red31 and Salvo have the correct answer. The problem is that the meter is made to read DC amps. The output of the controller is a pulse of varying width. The meter gets confused with this type of measurement and reads different current even though the average is the same.
Don't know if this will help.
On the WIRELESS tab click select. A list of sites will come up. From the list click on the circle to the left of the MAC address you want to select. Scroll to the bottom of the list and click Lock to AP (not Select).
Back to the WIRELESS tab. The MAC address that you selected should be in the Lock to AP box just under the SSID box. On the bottom of the WIRELESS tab page click Change button. Now at the top of the WIRELESS tab page there will be an Apply button, click it. Wait about 30 seconds for the Nanostation to re-boot.
Now go to the MAIN tab page to the right the AP MAC should be the one you locked to along with the signal strength.
Hope this helps.