Hi Kangmin,
The reason that properties is greyed out on the USB 6008 is because none of the properties this menu allows you to set are available on the 6008. For example, the properties page is typically used to set the accessory you are using, change power up states, and set RTSI cable settings. Since none of these features are available with the 6008, the properties page isn't accessible.
I hope this helps,
Paul C.