Accelerometer & Gyro

I was looking into useing the Accelerometer to do some eletrical magic.

But looking into the setting you can't put a "-" value in. How do the values on the Accelerometer

and gyro work. I thought if it is "-&+", that i would have to use a math channel and just add 3 or 5 the the value then if the value of that math is =<0 then do........