why rainbowduino got opposite negative and positive ?

I am using the "Rainbowduino LED driver platform - ATmega328" see as http://www.seeedstudio.com/wiki/Rainbowduino_LED_driver_platform_-_ATmega328 and I have decided to using a digital meter to check the voltage and it got me confused by the output the current from rainbowduino. It supposed positive number but i got a negative number. Why? If I want to change the digital meter to positive I would have to change from red clip to the blue wire of rainbowduino ( see letter red on rainbowduino which is negative number) . The image see the below. http://imgur.com/nCFiuY8

Actually, I am using the Funduino v1.0 not same as the other such as rainbowdunio, colordunio. Please help me thanks!

Where is the image?

Weedpharma

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p.s. the brown wire is TX are attched to Arduino UNO.

For voltages connect the black (COMM) lead to ground.

For current in, connect the red (+ve) lead to the +ve supply, black lead to the load (which would normally be connected to the +ve supply.